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so, it's no secret that GSC do not do well in 9th edition. It's not really that much of a surprise - shrinking the standard board size 6" on both ends and 2" on both sides removes 816 square inches from the formerly 3,456 square inch board size, greatly reduces the ability of a genestealer cult player to use the special rule that's been a massive fraction of the faction's power budget - Cult Ambush - to gain them any meaningful advantage. If you compare almost anything in the genestealer cult codex to anything from another codex you can see they pay a large tax in points for this ability. A great example is the Magus vs the Primaris Psyker - statistically and equipment-wise these units are identical, so we can see that GW is charging 35 points on top of the Primaris Psyker's usual 50 points just for the addition of the Cult Ambush and Spiritual Leader rules.

What then are the problems with Cult Ambush?

1) it is obviously a very powerful ability owing to its capability to essentially deliver a potent melee unit straight into melee with almost no response possible from an opponent, leading to basically everything in the GSC codex needing to be massively overcosted/underpowered in relation to other factions' units

2) the 9" restriction on it makes it much more difficult to use on min-size 9th edition tournament boards

3) it massively benefits some units (the glass cannon melee type units, of which there are several) and provides little benefit to others (mechanized neophytes, for example)

my redesign of the rule would be based on the classic board game Space Hulk, which was very good at conveying the atmosphere of the Terminators being hunted by a semi-determinate number of dangerous aliens. There was a good amount of play to the mindgames of the radar blips in that game, with both players getting to participate while the number of Genestealers was still not revealed.

Cult Ambush:

Rather than deploying any unit with this rule normally, the controlling player may instead deploy a Cult Ambush radar blip token on the board, or they may declare that the unit is setting up in ambush and place them into Reserves.

At the beginning of the command phase, any Cult Ambush radar blip tokens currently on the board may be revealed by the controlling player. Set up the unit on the battlefield. The first model set up must be within 2" of the Cult Ambush radar blip token, and all models must be set up outside of Engagement Range of all enemy models. Additionally, any models set up from a Cult Ambush radar blip token that was placed during deployment must be set up wholly within the controlling player's deployment zone.

At the end of the command phase, as long as the Genestealer Cult player has units with the Cult Ambush rule still in reserves, they may set up a number of new Cult Ambush radar blip tokens up to the number of units with the Cult Ambush rule currently in reserves on the board.

When setting up a Cult Ambush radar blip token, the token may be placed anywhere on the board more than 9" away from enemy models, or more than 3" away from enemy models that cannot draw Line of Sight to the radar blip token. Tokens are treated as models for the purposes of the Obscuring terrain trait.

If any enemy models end their move in a position where they are within 3" of and can draw line of sight to a Cult Ambush radar blip token, the controlling player must choose either to remove the token from the board, or set up a unit from reserves following all the normal restrictions on setting up units using a radar blip token."

Redesign Stratagem: A Perfect Ambush. Now 2CP. "Use this stratagem in the Shooting or Fight phase. Select a unit that was set up this turn using a Cult Ambush radar blip token. Until the end of the phase, re-roll failed hit rolls for that unit."

Redesign Stratagem: Lying in Wait. 2CP: "Use this stratagem when an enemy unit forces you to reveal or remove a Cult Ambush radar blip token. The first model in the unit may be set up within 3" of the token, and models in the unit may be set up in Engagement Range of enemy models."

Redesign Stratagem: Meticulous Uprising, 1CP: "Use this stratagem in the command phase of your first turn if your opponent won the roll-off to take the first turn. Move up to 3 Cult Ambush radar blip tokens up to 6". Units set up using these tokens must be set up wholly within 6" of the token, but do not need to be set up wholly within your deployment zone."

Redesign Stratagem: Scanner Decoys, 1CP: "Use this stratagem when placing Cult Ambush radar blip tokens at the end of the Command Phase. You may place up to 3 additional radar blip tokens on the battlefield this turn."

Redesign Stratagem: Prepared Ambush, 1CP "Use this stratagem when you set up a unit of Neophytes using a radar blip token. For the rest of the Battle Round, this unit may declare attacks in the Shooting Phase even if it is performing an Action, and add +1 to the result of all Saving Throws made by this unit.

Redesign Stratagem: Telepathic Summons, 2CP "Use this stratagem in the Psychic Phase. Select a <cult> PSYKER model from your army and a Cult Ambush radar blip token within 6" of that PSYKER model. That model cannot attempt to manifest psychic powers this phase, instead you may immediately set up a unit using that Cult Ambush radar blip token."

Add ability to Nexos: Strategic Co-ordination. for each NEXOS model on the battlefield at the end of your Command phase, you may set up 1 additional Cult Ambush radar blip token.

Add ability to Clamavus: Signal Scrambler. If an enemy unit ends their move within 3" of a Cult Ambush token while within 12" of a CLAMAVUS model, you may choose to leave the Cult Ambush radar blip token on the board rather than removing it or setting up a unit.




Automatically Appended Next Post:
Tl;DR Summary:

Rather than allowing units to be set up directly from deep strike, blip tokens will be set up throughout the game a full turn before units are set up from those blips, giving an opponent warning. For additional counterplay, if your opponent moves units within 3" of your blip tokens on the battlefield, you must either immediately set up a unit or remove the blip - and if your opponent has enough models to completely block off the blip you must simply remove it.

as a trade-off, once units are set up near blips, they are more free to move and act during the turn.

The intention of the rule is to push GSC ambush away from simply being a big no-counterplay alpha strike rule, as it currently is and always has been, and redesign it to be a rule that continues to be used throughout all turns of the game to keep an opponent guessing and responding to the threat posed by the blips.

Additionally, bear in mind that with the power of cult ambush somewhat cut back, units from the GSC codex like Purestrains, acolytes, aberrants, primuses, etc will be able to be given core stat buffs to account for the reliability of their alpha strike being somewhat cut down.

Will take a closer look later, but this is an ability that definitely needs some work, yeah. Also worth noting that 9e introduces Strategic Reserves. For a CP cost and a board edge, anyone can do the Ambush tango now.


Automatically Appended Next Post:
Okay, so it took me a few re-reads, but to sum up:

You use this ability instead of deploying a unit normally

It stays in Reserves, either as a radar blip, or in ambush

During deployment, set up a radar blip under normal deployment rules for each unit that's a radar blip

At the end of the Command Phase, you can deep strike a radar blip for each unit in ambush

At the start of the Command Phase (your Command Phase?) you can set up a unit from Reserves to replace a radar blip

You HAVE to do this immediately if an enemy moves close to the radar blip, or remove the blip

It's worth noting that you can currently, as-written, totally flood the board with radar blips; they don't go away on their own, and you get one for each unit in reserves at the end of each Command Phase. I assume this isn't intentional.

So the changes from the official version are:

You don't have to reveal "ambush" units in the first turn

Deep strikes from underground are slower and 100% predictable for a turn ahead of time, but allow the unit to still move around

You can "deep strike" VEHICLES, MONSTERS, etc.

I like the shell game principle you're working with, but it needs some tweaks for parsability if nothing else. I'm also a bit concerned that it doesn't interact at all with the "no more than half your units in Reserves" rule for Eternal War Matched Play. You'd want a note to that effect.

It's worth noting that this version is actually much more powerful for setting up assaults than the official version. The official version of "setting up underground" is just a standard Deep Strike, 9" limit and all. Almost every army can do it, Genestealer Cults are just the only ones who get it as a core, army-wide ability... well, them and Elysians. And effectively Militarum Tempestus. The official "underground" set-up allows me to place a unit of Aberrants 9.1" away from a target, then roll 2D6 to charge; that's 28% chance of a Charge, or 42% with Four-Armed Emperor. This version puts a delay on it, but it allows me to place a radar blip right in the middle of the board, then deploy a unit of Aberrants there in any future turn, strung out in any way I like, to any distance I like, so long as I'm not in Engagement Range. And then I still get to Move before I Charge. That's absolutely bonkers; I can set up 20 Acolyte Hybrids using this, with the first guy anywhere within 2" of the blip (2" radius) the second guy anywhere within 2" of him (5" radius) and so on, for a potential threat radius covering basically the entire board, and I still get to Move, Advance with the Genetic Lineage Stratagem, and Charge 2D6. That's a total threat radius of more than 65+3D6".

Apologies if this is too presumptuous, but I took a shot at reworking your rework, with your stated goals in mind. Happy to move it to its own thread if you'd rather not have it here:

Cult Ambush
Genestealer Cults plan meticulously before rising up against their oppressors, remaining hidden until the moment of ascension arrives.

During deployment, you can set up a unit with this ability in ambush instead of on the battlefield. Units set up in ambush do not count towards any limits that the mission you are playing places on the maximum number of Reinforcement units you can have in your army, and can be set up as Reinforcements in the first battle round regardless of any mission rules.

During deployment, you can set up an INFANTRY or BIKER unit with this ability underground instead of on the battlefield.

In addition, ignore the Power Rating of units with this ability when calculating the Command points cost of placing units into Strategic Reserves.

Radar Blips

When you set up a unit in ambush, you must set up 1 Radar Blip anywhere on the battlefield that is wholly within your deployment zone, or anywhere on the battlefield that is wholly within 6" of a battlefield edge and more than 9" away from the enemy deployment zone and any enemy models. A unit embarked within a TRANSPORT that is set up in ambush counts as 1 unit for this purpose, but both the TRANSPORT and the embarked unit(s) must have the Cult Ambush ability.

When you set up a unit underground, you can set up 1 Radar Blip anywhere on the battlefield that is more than 9" away from the enemy deployment zone and any enemy models. If you do not, keep that Radar Blip to one side – this is your Radar Blip pool.

At the end of the Reinforcements step of your Movement phase, you can remove any number of Radar Blips you've set up on the battlefield and return them to your Radar Blip pool. You can then set up any number of Radar Blips from your Radar Blip pool anywhere on the battlefield that is more than 5" away from any enemy models.

A Radar Blip is an Area Terrain feature, 1mm in height with a footprint of 1", as described in the Warhammer 40,000 Core Book. When measuring to or from Radar Blips, always measure to the centre of the marker. Until the first turn begins, any Radar Blip you set up is treated as a model from your army.

Revealing Radar Blips
When you reveal a Radar Blip, select 1 unit from your army that you set up underground. If it is the first turn, select 1 unit from your army that you set up underground or in ambush. Set up the unit you selected anywhere on the battlefield within 3" of that Radar Blip and more than 9" away from any enemy models (any models that cannot be placed are destroyed), then remove that Radar Blip. If the unit you selected was set up in ambush, it must also be set up wholly within your deployment zone or wholly within 6" of a battlefield edge.

If the unit you selected is a TRANSPORT, any units embarked within it can immediately disembark after it has been set up on the battlefield. These units are set up exactly as though you had set them up by revealing the same Radar Blip.

You can reveal a Radar Blip under the following conditions:

The Uprising Begins: At the start of your first Movement phase, or the end of your opponent's first Movement phase (whichever comes first), you can reveal any of your Radar Blips. If you do, the unit you select must be set up wholly within 6" of that Radar Blip, and more than 9" away from the enemy deployment zone. Such units can move normally on that turn (i.e. Normal Move, Advance, Fall Back), and are considered to have Remained Stationary if they do not.

Spring the Trap: When an enemy unit ends a move within 6" of one of your Radar Blips, you can immediately reveal it. If you do, you can set up the unit you selected anywhere on the battlefield that is more than 3" from any enemy models, instead of more than 9" (other restrictions still apply).

Subterranean Assault: At the start of the Reinforcements step of your Movement phase, you can reveal any of your Radar Blips. If you do, you can set up the unit you selected within 6" of the Radar Blip, instead of within 3".

Stratagems wrote:They Came From Below (1 CP)
Use this Stratagem before you reveal a Radar Blip. Select up to 3 INFANTRY or BIKER units from your army that are set up in ambush, and set them up underground instead. You can also remove up to 3 of your Radar Blips and return them to your Radar Blips pool. You can only use this Stratagem once per battle.

Meticulous Uprising (1/2 CP)
Use this Stratagem before you reveal a Radar Blip. Remove up to 3 of your Radar Blips and return them to your Radar Blips pool. Then, select up to 3 Radar Blips from your Radar Blip pool and set them up anywhere on the battlefield that is more than 9" away from any enemy models or the enemy deployment zone. If you set up each of these Radar Blips wholly within your deployment zone, this Stratagem costs 1 CP; otherwise, it costs 2 CP.

Scanner Decoys (1 CP)
Use this Stratagem when you set up a Radar Blip. You can set up 3 additional Radar Blips, following the same restrictions; if you do not, add them to your Radar Blip pool instead. You can only use this Stratagem once per battle.

Telepathic Summons (1 CP)
Use this Stratagem at the start of your Psychic phase. Select a <CULT> PSYKER model from your army. That model cannot attempt to manifest any psychic powers this phase. Instead, roll 3D6; you can add one new <CULT> INFANTRY or BIKER unit to your army if it has the Cult Ambush ability and its Power Rating is equal to or less than this roll (otherwise, no new unit is added). This unit is immediately set up underground. Then, reveal a Radar Blip within 18" of that PSYKER model, or set up a new Radar Blip within 18" of it.

Return to the Shadows (1 CP)
Use this Stratagem at the start of the Reinforcements step of your Movement phase. Select one INFANTRY or BIKER unit from your army that has the Cult Ambush ability and is more than 3" away from any enemy models. Remove that unit from the battlefield and set it up underground. Then, add 1 Radar Blip to your Radar Blip pool.

Lying in Wait (2 CP)
Use this Stratagem when you reveal a Radar Blip. When setting up the unit you selected, it is set up using the Spring the Trap condition. However, the unit cannot declare a charge this turn.

Your rework cuts out some of the intentions of the change

1) Subterranean Assault would not be a thing. The intention is to remove universal deep strike as a crutch of the army to lean on, and replace it with a version of cult ambush that increases interaction with your opponent.

2) You appear to have removed the ability to return the blip to the blip pool rather than placing a unit down (in "spring the trap"). The mechanic relating to line of sight, and therefore treating the blips as models for the purposes of drawing line of sight, is also removed.

3) the restriction of setting up wholly within 6" and over 9" from enemy models is overly restrictive given the turn of warning an opponent has to react to any placement of blips.Additionally, keep in mind you may have up to 20 acolytes deploying around a single blip. 9th edition's unit coherency rules are more than enough to limit shenanigans relating to 'daisy chaining.' If I playtest it and find it's too easy to daisy-chain models in large units from blips, I may add the additional restriction that units must be in base to base contact when deployed - there should be no possibility of significant advantage.

4) I did intend to add the capability to arrive via radar blips to VEHICLE keyword models as well. VEHICLE models may now be universally outflanked via stratagem - it seems silly to continue to exclude vehicles from participating in the ambush the rest of our units are supposed to be springing.

 the_scotsman wrote:
1) Subterranean Assault would not be a thing. The intention is to remove universal deep strike as a crutch of the army to lean on, and replace it with a version of cult ambush that increases interaction with your opponent.

Oh? I think I must have misunderstood, then; your version still allows the GSC to place a Radar Blip anywhere on the board, then deep strike onto it next round. That's how this one works, too; you can only set up/remove Radar Blips at the end of your Reinforcements step, but Subterranean Assault takes place at the start of your Reinforcements step, so you can't put one down on the same turn that you reveal it. Isn't that the intent? To defang universal deep strike a little by giving the enemy "advance warning"?

 the_scotsman wrote:
2) You appear to have removed the ability to return the blip to the blip pool rather than placing a unit down (in "spring the trap"). The mechanic relating to line of sight, and therefore treating the blips as models for the purposes of drawing line of sight, is also removed.

That was a deliberate change, yeah. The line of sight mechanic was cool, but would be very board-dependent, and more importantly felt like it opened the door to a lot of shenanigans, e.g. transport positioning, or staggering ambush reveals somehow. I was reminded of characters being rendered impossible to shoot due to an ally lurking behind a nearby wall. Removing that led me to reframe the "they're on top of you, trigger or remove" mechanic into more of a deliberate "trap/tripwire" effect; aside from the standard first turn ambush reveal (which you can also do as a "concealed positions" deployment for underground units), your blips are basically a slow, telegraphed deep strike. But, the upside is that they also act as a 3" radius bubble, where the opponent risks triggering a monster mash if they move into certain parts of the battlefield. It encourages area denial and mind games and literal ambushes, rather than trying to finagle your way out of line of sight for a sneaky charge.

The "remove" choice isn't there because it doesn't mean much; you can manually remove and replace the tokens on your turn anyway, so I'm fine with letting the player just leave them on the board if they don't want to trigger a "trap" right now.

 the_scotsman wrote:
3) the restriction of setting up wholly within 6" and over 9" from enemy models is overly restrictive given the turn of warning an opponent has to react to any placement of blips.Additionally, keep in mind you may have up to 20 acolytes deploying around a single blip. 9th edition's unit coherency rules are more than enough to limit shenanigans relating to 'daisy chaining.' If I playtest it and find it's too easy to daisy-chain models in large units from blips, I may add the additional restriction that units must be in base to base contact when deployed - there should be no possibility of significant advantage.

The "wholly within 6" bit was taken from the existing Cult Ambush rules (and only applies in that same, first turn set-up situation), so if it's not a problem in 9e then it's not a problem. Easy to remove; I suspect it's mainly in there to ensure that units are actually where the ambush marker "says" they are on an ambush, as opposed to making a weird formation that slightly nudges it.

As for keeping in the "more than 9" away" part... I guess that's a misunderstanding on my end? I thought the intent was to neuter the Universal Deep Strike by gating it behind a prep-turn; no first turn Deep Strike, and the enemy knows roughly where they'll show up (if they do). That means the utility gap between "ambush" and "underground" is lower, so units with Cult Ambush can be costed more cheaply. Is the intent instead to make the Universal Deep Strike more predictable, but potentially more powerful if you can control/predict the enemy's movements, since you can drop in regardless of enemy distance?

 the_scotsman wrote:
4) I did intend to add the capability to arrive via radar blips to VEHICLE keyword models as well. VEHICLE models may now be universally outflanked via stratagem - it seems silly to continue to exclude vehicles from participating in the ambush the rest of our units are supposed to be springing.

Honestly, it might be as well to just say that GSCs can do Strategic Reserves for no CP cost. Covers that base really easily.

Didn't read the whole thread but it doesn't really to step away that much from the current iteration, just remove the "deployment zone" limitations and have token be put all over the board but with the >9" enemy, meaning you're using the same rule Marines have but deploying tokens instead of actual units (same "revealing tokens" rules apply)

KurtAngle2 wrote:
Didn't read the whole thread but it doesn't really to step away that much from the current iteration, just remove the "deployment zone" limitations and have token be put all over the board but with the >9" enemy, meaning you're using the same rule Marines have but deploying tokens instead of actual units (same "revealing tokens" rules apply)

i do not think allowing army-wide turn 1 charge any time you win the roll off to go first would result in particularly good or fun game design.

Our units would likely still have to be comically gimped in relation to other units that cost similar to them (insert hilarious Aberrants vs Any Other 35Pt Unit statline comparison here) and many opponents would probably, with good reason, just ask to re-rack and start over after the first turn if they lost the roll off.

 the_scotsman wrote:
i do not think allowing army-wide turn 1 charge any time you win the roll off to go first would result in particularly good or fun game design.

Our units would likely still have to be comically gimped in relation to other units that cost similar to them (insert hilarious Aberrants vs Any Other 35Pt Unit statline comparison here) and many opponents would probably, with good reason, just ask to re-rack and start over after the first turn if they lost the roll off.

I really like that your initial post included your stated design problems with Cult Ambush. I think it might make sense to do the same with what you want to achieve when reworking it, just bullet point that out, because there's some commentary below your post, but it's not nearly as clearly stated. My understanding is that you want:

To lessen the power of "underground" deployment, i.e. free deep strike, because it acts as a surcharge on the whole army, even though only half tops can use it.

To increase the interactivity and potential uses for "ambush markers", so they're not just tossed out after the first turn, and Cult Ambush stays relevant.

To make "ambush" (i.e. non-deep strike, if there's a difference in this new version) deployment more useful for a wider range of units, e.g. mechanized troops.

To make it easier (but still balanced) to use this ability to deploy units within 9", because current board sizes make that bubble harder to avoid.

To further enable and encourage the mind games and area control that Cult Ambush already permits.

Is that about right? Am I missing any design goals?

I don't know if it's healthy to allow the entire army - as seems to be the case in your rewrite? - to be kept in Reserves basically indefinitely, then all get dropped on the last round. I appreciate that there is some counterplay, in that the opponent can track down or anticipate ambush markers, and that objective-based gameplay makes this a dubious strategy a lot of the time... but it still seems like a recipe for not-a-lot-of-fun. At the end of the day, my opponent came here to play a game of Warhammer, not a game of Space Hulk. Flavouring my abilities around mind games and "chasing me down" is cool, but fundamentally changing the way the game is played... less so.

If you keep your army sitting in reserves until turn 5, the balancing mechanic to that is that you lose the game. AFAIK theres not a whole lot that prevents me as, say, a space marine player, to take my whole army and drop pod up and just sit there with all my army except for one unit in reserves, the only thing is that I do lose the game if I do that.

Basically, you've nailed down the main things I want to achieve. The core concept of GSC gameplay - that the GSC are always launching some kind of ambush, that's the core of their army identity and what playing against GSC should 'feel' like - is really cool, but the execution has never not made them into something of a one-note army.

When we were tied to some ultra-random table, that note was 'take many small squads of units, rely on the ultra-random table result that's crazy good and OP to offset the results that were really bad'. When that randomness got removed, there was no brakes on the "dedicate your whole army to the super crazy alpha strike from deep strike reserves" train.

And while the virtually identical units of Metamorphs/Aberrants/Acolytes/Purestrains duke it out in iteration after iteration of the rules you've got a full half of the roster that's just sitting around awkwardly as 'basically dark eldar kabal gameplay, but shittier because all your stuff is BS4+ and doesn't have the invuln saves and hit mods dark eldar do'

The concept for gsc has always been amazing, but even when theyre competitive theyve nver been particularly good to play against.

 the_scotsman wrote:
If you keep your army sitting in reserves until turn 5, the balancing mechanic to that is that you lose the game. AFAIK theres not a whole lot that prevents me as, say, a space marine player, to take my whole army and drop pod up and just sit there with all my army except for one unit in reserves, the only thing is that I do lose the game if I do that.

Okay, fair enough. I do think there's probably a reason the "no more than half" rule exists in Matched Play - flashbacks to the White Scars getting tabled in turn 0 by Kroot - and it probably has to do with not wanting to waste the other player's time. If I'm up against a Cadian gunline and keep everything in reserves on the first turn, they're just... left to shuffle around a bit. No shooting, no fighting, no charging, no playing the game. This is especially bad if it's their first turn, because I'm effectively getting a "free turn" of not being shot at or charged, by anyone, ever. It's a free Prepared Positions on steroids.

Even if it's not competitive due to the new Objective rules (and bearing in mind that future missions might not use those), it's still not the fun or intended way to play.

With that in mind, I'm going to take a look at the restrictions the game puts on Deep Strike/Reserves (or Concealed Positions, which is effectively a turn 0 Deep Strike).
1) No more than half your army by models/points can be in Reserves at game start.

This is clearly intended as a "both players actually play the game, please" rule, and/or insurance against weird niche scenarios down the line.

It stops you just ignoring who gets the first turn and deploying after the enemy has spent their turn doing nothing.

Drop Pods can ignore this, so there's room to negotiate here. There's a points cost on it.

2) Must be set up more than 9" away from enemy models, and more than 9" away from enemy deployment zone if it's the deployment phase.

This is basically universal, and is an anti-melee rule, designed to curb the power of Deep Strike melee deathbombs by requiring a charge roll of 10+ on the turn it's set up (1-in-6, up to 1-in-4 with +1, 1-in-3 with a reroll, 1-in-2 with both).

The motives behind the deployment version is less clear, but the deployment zone part is probably to avoid edge cases with objectives etc, and the enemy distance is probably to make it easier to run away from an "infiltrating" unit if you get the first turn? Also tends to apply to units that get a free "Scout" move.

Some units have a variation on the deployment zone restriction. Tau Stealth Suits can be set up anywhere outside of the enemy deployment zone, but more than 12" away from enemies.

Exceptions are rare but exist; Precision Drop and Daring Descent are 1CP Stratagems that allow 5" deep strikes, but only on non-melee Tempestus.

A common exception is "cannot charge this turn", for the exact same reason. The Mawloc can set up "more than 1 inch" away, but can't charge, for example.

"Disembark after movement" Stratagems and abilities almost always come with the Can't Charge caveat; Hold On, Boyz (Orks) is 2CP, Reckless Maneouvre (GSC) is 1CP with casualties, Lightning Debarkation (White Scars) is 1CP, and Assault Vehicle is innate to the Impulsor. Skystrider's the only one without this caveat, and it works only for a Warlord.

Webway Ambush is a big one; a 1CP Stratagem for Harlequins that lets you set up a unit anywhere more than 1" from an enemy, so long as it's wholly within 3" of a Webway Gate. No other restrictions, though a Webway Gate itself can't be set up within 12" of an enemy deployment zone.

3) Can't deploy in the first battle round.

Mostly just the same as 1) - deploying in the first battle round removes all the "downsides" of putting a unit into Reserves, namely that you don't start with it, so it comes in later.

So, let's go back to that list of priorities and see what we can use. It's easy to weaken free deep strike; you can forbid charges when it's used, or give it the delay and "warning" of an ambush marker, or both. It's definitely possible to deploy units despite the 9" enemy bubble; it's not common, and it requires other conditions or costs (e.g. Strats, no charging, static marker, specific unit). Ignoring the "deployment zone" restriction also calls for a different condition, but is much easier. Keeping Cult Ambush relevant past the first turn, and allowing for more mind games, depends entirely on the specific implementation of it.

The really tricky one, as far as I can see, is making Cult Ambush more useful for non-melee (and mechanized) units. This basically won't happen through the ambush ability alone, IMO. It's too complex a result, and all the benefits of ambush (avoid being shot at, deploy closer to the enemy, bypass obstacles when "moving") directly favour armies that want to get up close and personal. This will need to be an emergent change stemming from other abilities, units, and costs that benefit from ambush, despite not being melee. For example, more weapons and Stratagems and auras that massively favour being within half range and/or being set up this turn, or that benefit from having a unit in a place that would normally be tricky to get to. The exact opposite of Prepared Ambush, basically! Examples might be:

Barrage From The Shadows (1 CP)
Use this Stratagem in your Shooting phase, when you select an <CULT> INFANTRY or <CULT> BIKER unit from your army to shoot that was set up or disembarked in this battle round. Until the end of that phase, autopistols models in that unit are equipped with have a Type characteristic of Rapid Fire 1.

Deadly Crossfire (1 CP)
Use this Stratagem in your Shooting phase, when you select a <CULT> INFANTRY or <CULT> BIKER unit from your army to shoot. Draw a straight line between the base of one model in that unit, and the base of the closest model in another <CULT> INFANTRY or <CULT> BIKER unit from your army that is within 18". If this line passes over any enemy units, those units are marked. Until the end of that phase, when resolving an attack made by that unit a marked enemy unit, add 1 to the wound roll.