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Apologies if this is in the wrong area, but I am coming back to 40k after not playing since early 6th edition and I am thinking of building a new 40k imperial army for play at a club. I have some general ideas - but as I yet don't understand the finer points of a lot of the rules, I have no idea which of these ideas would be useful.

This began as me hearing some of the fluff for Imperial knights and thinking that this would be a great basis for building a 40k bretonian style army.

What I would like to include in a 2k army list:
One or more Dominus patern knight- these look super cool, and their cool factor is a good proportion of why I want to start draining my bank account again.
One or more Questoris pattern knight- the above applies here.

For both of these I like the look of the closer ranged one. The Valiant with the ridiculous harpoon, and the Gallant. I'd be interested in including both, but I'd rather not spend the money if it turns out that they are just going to be less effective than other £100 models.

One or more unit of helvrins/warglaives - the are kind of ugly, so I'd like to put some thought into making them look asthetically like things that lesser nobles would want to use

I've heard that people use allied imperial gaurd to get command points- as yet I don't know how sensible it is to do this, but I'd like to include a slightly weird group of IG to represent the lowest ranks of nobles and the peasant millitia.

A large number of Death Riders/ or Rough riders representing the bottom ranks of nobles. These would probably be conversions based on classic bretonian miniatures/empire knights/demigryph Knights/cold ones.

Am i right in thinking that their special rules mean that they can arrive on an opposing players table edge, and charge on the turn that they arrive?
Also if I take knights that would be charging would there be an issue with them blowing up and killing my horsemen?

A large number of regular gaurdsmen converted from old bretonian/empire miniatures representing the bottom rank of peasantry. Possibly a tank or two representing representing the squires of a particularly wealthy lord.

If there was a way of including the old Karl franz/leon leoncoeur models I'd like to do that but I have no idea what it could represent, and similarly If there was a way I'd like to include some old pegasus knights - but I have no idea what they would represent.

My questions are what would you include on this kind of list? why? would you include those things? and how would you play it on the tabletop?

______________________

I also have an old demonhunters/ grey knights army - so if i was to try and put this together, probably my first experience playing these new units would be alongside these- so bonus points for suggesting something that would synergise with these.

So cool!

So .. I would include the Roi Soleil himself, the big kingpin in his castellan knight (its much better than the shorter range one) as the first 700 ish points of the army.
His son is in either a warden or a gallant (both fair choices, I reckon, or the slightly pricier crusader (very shooty, so I suggest taking the least shooty of the three to balance the big guy out).
He is attended by a pair of knights, both high ranking nobles, who, not being royals, have to content themselves with warglaive and helverin, respectively.
That's the knight side. It gives you some godpowerful smackdown from the big guy, at longer ranges, and its got some decent melee in the gallant + warglaive, and the helverin sort of tries to look invisible while deleting light enemy armor. Something like 1400 points, ish.
so ok.

Minor nobles are stuck in the most HORRIBLE of machines, the scout and armored sentinal, the fighting melee sentinal (forgeworld but easy to proxy if you build one with a big claw and no gun) and even an elysian drop sentinals with a multimelta gun or heavy bolter (if you really wanted to go there)

Maybe 6 total, all of them bristling with sentinal chainswords and a variety of not so expensive but decent weapons (plasma cannons and missle launchers, mostly), and painted up in gaudy, medieval looking noble crests of armor and symbols of tyranny, etc etc. A colorful circus of minor nobility, you can get for about 260 points, ish. That brings you to about 1660ish, leaving 340 for the rabble.

company commander
lord commisar (find some fat noble or clergyman from the bretonian game and give him a commisar hat, bolterpistol, and powersword.
ministerium priest (what noble would possibly go to war without a priest nearby?)
that's 110
230 left
30 for an engenseer. With so many knights and little mechs, he will be busy!
court astropath! Cause whynot!
175 left for 3 units of gaurdsmen armed with various weapons, mostly, though, grenade launchers and flamers, cause themeatic.

That leaves you enough for one command squad of the dkok riders, I think, ish. rough riders have incidentally been relegated to legends.

You can get a lot more rough riders if you lose the armiger (either one) and buy a squad or two of them or the dkok types.

Now, also remember 5 crusaders (come on man, knightly squires with powerswords and shields in the service of the great mecha) can also be done, and also painted up as insanely colorful lesser nobility. You could do for example.
You break the rest down into "major houses" and "minor houses" which is purely aesthetics, not detachment nor gameplay, like ...
House Monram (Or, a lion rearregardant gules) (This is painted on the knight gallant, perhaps, or on the helverin, a good knight for a cowardly, if wealthy, noble family's leader)
5 crusader squad of house monram (same pattern painted in minature with slight variations on each of their shields. Indicating first son, cousin It, whatever, but all related minor nobility)
10 man regular gaurd squad of house monram levies (same colors but not a particular pattern)

A second noble house has also sent its troops and leaders. They are under the command of the warglaive, which is painted in a truly gaudy mix of light blue and bright red, with a shiny silver axe on a copper haft drawn on its main armor body. On the axe, a black falcon with bloody claws sits ready.)
House Hart (Az and Rg, quartered, with 3 falcons sable and a gold axe, one per quarter, would be the "root" heraldic thing I am thinking of. So everything in the Hart troops uses those colors and symbols and you try to get a lot of axes in the troops, too.
Gosh, ok, so its been YEARS since I had to do heraldry and I don't remember much, but the point is, you make a couple differfent such patterns and have 1 or 2 of the armigers or sentinals match the pattern of the levies they bring, then give them a few knights (a good house) or a squad of regular gaurd (a poor house) or a squad of veterans. You can put the various subunits in the same color scheme, like the blue and red of the quartered field of the oddly named house hart above, would mean you paint those poor troops in a lively blue and red, with black splotches and a black bird on the flag or occasional infantryman's shield.

Another house miught have very simple livery -- just a yellow and white quartered shield with three red dots on it, but that would be enouhg to give your poor infantrymen a garish yellow tunic, yellow backpack, white pants, and red caps and boots. Would be humiliating if they were not obviously servants of the Knight Gallant -- whose very simple heraldic design indicated a very old and thus less "complex" house, albeit one that had intermarried with a second very old and not very complex house. The oldest nobility got to get really simple shields, and it became more complex as inermarriages caused people to pictorially show the colors of BOTH houses (hence quartered shields, halved shields, etc) and begin to show various symbols to differentiate the 13th from the 12th earl of that line, etc etc. So if someone's shield is like, White, with a red deer looking at the sun, its pretty simple and he is probably no minor noble. If its like, quarter white, quarter red, 3 ducks in onequarter, 3 coins in another, a man being hanged in the third quarter and a boat in the fourth, you should be thinking this is some late to the party nobility -- married well, sure, but not the root on which a dukedom or kingdom hangs. (Please, you professional heralds, be merciful in my broad brush discussion here! And yeah, I know BEANS about heraldry in the year 40k, except that skulls fitgure in it a lot.

Obviously, you can get a lot more servant units if you downgrade the dominus to a questoris .. one of the classic duos is a crusader in the back and a gallant up front, with a pair of armigers. That would free up a whole bunch more points for a small detachment of grey knights, or to make more gaurdsmen with their various special weapons, or perhaps, a couple garishly painted basilisk and wyvern type weapons. Altouhg to be honest I think that a pair of griffin mortar carriers would be AWESOME looking with this army.

Hmm.

House Royal
Knight Crusader with cheapest (I think its 490ish) rig (4++ shield constantly on) (Red, Gold, Yellow with Yellow being the major color, perhaps.)
Knight Gallant with sword (around 380 now, I gatrher) (2+ armor trait rather than a buffed up shield, as he is going into arms lenght battle and the knight shields don't work there very well) (Red, Gold, Green)
Armiger Warglaive
Armiger Helverin
Now that would leave you like 800 points to play with.
So.
company commander
ministerium priest
lord commisar of the realm
3 x 10 regular gaurd (a special weapon or heavy weapon per squad, to keep cheap)
2 x 10 veteran gaurd (mostly grenades and missle launchers, I think, and shotguns) (One in the royal colors, and one in a mix of brown,grey.black, and red to make them look like mercenaries.)
1 engenseer
1 astropath (the court has a seer!)
1 special weapons squad with 3 meltas
6 crusaders in a squad
2 crusaders in a squad

That's 590ish, if my math is more or less I am not looking this all up irght now accurate.

So you have about 210 for maybe 3 sentinals and a griffin mortar carrier,

In my head it looks gloriously medieval -- like six distinct patterns of garish troops (and a couple regular gaurd squads in brown with darker brown and a little grey as "mercs" darting in and out to seize objectives while the huge knights blast asway at the enemy.

Thanks!

That was exactly the kind of help that I was looking for, and that army would look great on the tabletop. I especially like the idea of different houses in different colours- painting lots of different and really distinct heraldry was something I really loved about the old bretonians, and I think it really helps with the narrative idea that this is a civilisation coming together to defend itself from whoever I'm facing on the tabletop.

[or rightfully anex their territory]

I was also thinking I could use not just the old plastic men at arms but also empire halbadier kits - so the different units could each represent different kinds of people coming to the battlefront - maybe bretonians as country folk and empire kits as fancy city types.

Follow up questions:
Where can I find the rules for dkok? And is it an issue if they are from some old FW book?

I think I understand command points and formations in this eddition- is that a superheavy detachment and a battalian?

Why did you go for so many Gaurd Infantry? Are lasguns more effective now?

Whats the best way of keeping track of the changing points of miniatures?

I bought the Canis rex kit, am I right in thinking I could magnetise it so that I could exchange arms and run it as all the different kinds of questoris knights?

Gaurd infantry dies so easy, you want enough of it or it ends up not doing much.
The index : armor forces of the imperium is the book that elysians, dkok, and other forgeworld models come out of (like the griffin mortar carrier artillery piece). Its being rewritten so the rules are up in the air right now.

As detachments go, you need one for the nights -- that has to be a superheavy detachment or a lone superheavy auxilliary, no other choices. So its either 3 knights minimum or 1 lone knight. Armigers can come in squads so you can put two in a slot as "one" knight if you have to.

You then need one for the guard.
Battalion needs mininum 2 command, 3 troops, but can carry up to 3 command, 6 troop, 6 elite, 3 fast attack, 3 heavy.

3 sentinal types (the melee one is also a forgeworld index one, it thererfor will also come from the rewritten forgeworld index forces of the imperial armory soon) can also be squaded up, so you can use fast attack for sentinals (slot one, slot 2) and for some dkok infantry.

Now the fine point of this is, as the rules HAVE been written, elysian (drop troop) or death korps (WW1) don't lose their special rules when stacked with other gaurd, but other gaurd loses their rules when stacked with elysians.

So if you mix death korps of krieg into the battalion detachment of infantry, your cadians won't shoot as well, or your infantry becomes "generic". This doesnot effect the crusader or ministerium priest or astropaths either way -- they are "truly neutral" to other regiments.

So ..
3 knights in a big detachment (basically pick 3, or 2 bigger knights and 2 armigers, or even 1 big knight and 2 separate non-squaded armigers) ..

2 commanders (minimim) and 3to6 gaurd troop choice = a battalion. But I (in my example) filled it with astropaths, crusaders (note that if you have a ministerium priest you can bring multiple units of crusaders without them counting against your maximum of elites, they are "nonslot" items.)
You could also have fairly cheap troops in livery colors firing heavy weapons (gaurd mortars are fairly widely respected even if they are not as great as they used to be) or heavy bolters or missle launchers or even lascannons.

Now some coolish ideas.
Scions have 7 point per scion elite gaurd troops with 4+ rather than 5+ armor and -2 ap hotshot lasguns, who can deepstrike. 5 man squad of scions painted up in feudal colors is a pretty decent little unit some house could bring as a cheap (35 points!) troop choice beside a squad of veterans (also good at shooting) with grenades.
dKOK has another unit for you to consider which is basically a flightless scion .. the stormtrooper. They cost a bit more than normal infantry but each 5 man squad carries 2 special weapons (much like scions) and has a 4+ armor, with NO jum pack. You could proxy these pretty easily by putting special weapons on 2 of 5 scions, and a bolter pistol on the sgt, and then slipping a pair of gaurd lasguns onto two scions. Just don't put the backpacks scions usually have on the models, and viola, you ahve built a cheap, plastic (not resin) proxy for the stormtroopers, which are a fairly elite and uparmored version of dkok troop choice.

So you could have an army with 2 regular (80 points) crappy i10 man regular gaurd, 2 x 5 scions troop choices (one plain and one very elite with a pair of melta to hunt knights), and 2 x 5 man dkok stormtroopers. This would give you even without any bretonians a dizzying array of very different gaurd infantry, when you then put a trio of crusader units behind them. (I use a very medieval looking conversion of a crusader from an old chaos warrior, you can see it in my pictures section, I think, and the guy with the big axe is my ministerium priest).

Point is, you got an army that is now a sea of different units and colors, and those infantry hold objectives, hide behind terrain, do all the little people jobs that the big knights are terrible at, while the big knights try to delete the enemy armor and flyers and elite infantry.

There is an annual points update that comes out you can buy -- last one was from the 2019 update. Most people keep track of minnature prices by using battlescribe (which is an alternative sourced app for your phone that someone updates. I dunno, I don't use it.)

Canis rex kit I have neither seen in play nor looked at the kit.


Anyway. 3 detachment limit at present, and it will be much harder to have detachments extra in 9th edition soon.

so you basically got 1 superheavy : knights (this opens the knight strategies) and 1 gaurd detachment minimum. Realistically, you really want to put the dkok and elysians in a separate gaurd detachment. That way your main bulk of soldiers will get (for example the cadian infantry all reroll 1's if they don't move, which is nice shooting.)

If you can find an index armory book, I think a blend of dkok stormtrooper units (proxied by people in heavier looking armor with lasguns) and scions (whose deepstrike mobility means someone spent a lot of money equiping his house!) and just plain old gaurd (to use as things like veterans) give you a nice counterpoint to a mob or two of conscripts in mostly bretonian plastic. Note that conscripts suck this edition cause they don't take orders well, which cuts their firing by as much as half.
You could have a few heavy weapon squads in the back, a mix of actual gaurd squads -- but you get one cadian, one catachan, and one DKOK squad and viola, you have 3 different houses whose troops are subtly differntly equipped and you paint them up in different colors. Or you mix and match parts from the squads to create unique troops (in my pictures section is a guy holding a wierd gun who is nothing more than a marine backpack on a cadian soldier with catachan arms and a modified lasgun with a grenade launcher on it. He is an elysian paratrooper leader -- and looks pretty different from any of the models I just stole parts from. I bet you can do all sorts of stuff like that to make your gaurd into gaurd, but it won't look like any gaurd anyone has seen, EVEN if you don't get a bunch of heads from mad robot or statuesque.

Canis rex works well with a pair of helverins minimum. You could run your army with
Gallant (melee only!) (Canis rex) (2 helverins) as the superheavy, and it wouldn't be the most comptietive in history, but it wouldn't suck and you have coverd shooty and melee functions for the big knights.

There is a kit called "renegades" with 2 questoris knights in it that you can buy that has all the little weapons. IF you score that, you have 3 questoris and you could even go
gallant or warden
warden or gallant
canis rex
2 armigers
for about 1300 to 1400 points, leaving 700 to 600 left ot buy up the feudal follower army.

It sort of will hang on how many points you wnat to stick in minor nobility (sentinals are such a picture of that!) and elite house infantry, special infantry like heavy weapon squads or special weapons squads and vets, and command squads, and advisors .. ie, the knights brought their court with them, vs how many points go into regular gaurd rabble conscripts, regular gaurd troop infantry, which would give the army a much bigger "my court brought the peasantry every last one to try to stop this threat, rather than its a party the foolish king wants to throw while showing everyone how great HIS armor is as he smites the tyranid horde single .. GOOD GOD HOW MANY TYRANIDS ARE THERE? "

Very different psychological feel to it, I think.

Thanks so much for helping!
I really like the conversion- the feel you've got is exactly the one i'd like to do with this army. Although Now I've written the first list I am starting to bawk at the number of conversions I'd have to make

(downloads battlescribe)

Now I can see the points costs for units making selections is starting to make a bit more sense.

Here is my current list. It’s a little over at 2145 – so it needs some fat trimming, and it may well be that I am basing some selections/ideas for tactics on misunderstanding the rules.


Imperial Guard Battalion 932 pts

HQ:
Commisar Yarrick 100pts
Company commander with boltgun 31 pts
Company commander with boltgun 31 pts

I’m imagining these as knightly conversions. Probably all three with unique heraldry

Troops:
Infantry squad with autocannon 50 pts
Infantry squad with autocannon 50 pts
Infantry squad with flamer 46
Infantry squad with grenade launcher 43
Infantry squad 40
Scions 35

I really like the idea of infantry squad each based off different oldhammer plastic kits, and be painted in the colours of different nobles. I also like the idea of mixing in some more modern gaurd miniatures.

If I could get ugly medieval helmets (like pigface bascinetts) that could really add to the look of some of these units.

Your right about the scions- they would add to the feel and be an effective unit in lots of ways. As I am low on points perhaps there is a case for switching another infantry squad for scions.

I liked the idea of mixing 40k kits for regulars and wh kits for conscripts, but according to battlescribe its no cheaper per model for conscripts even though they are worse; so despite the feel i think I am going to have to not use them.

Elites:
Commissar 16
Crusaders (x2) 26
Crusaders (x2) 26

One squad of crusaders would be with Knightly Yarrick, and dressed in his colours, perhaps another with a company commander.
Am I right in thinking that if I have two units of crusaders I would get two acts of faith at the start of every turn? Even just one act of faith I think would be enough to make a knight valiants harpoon much more predictable and thus much more useful.

Fast attack:
Rough riders with Plasma gun 65pts
Rough riders with Plasma gun 65pts
Scout Sentinel with multilaser and chainsaw 37pts
Scout Sentinel with multilaser and chainsaw 37pts

This is probably the part of the list where my grasp of 8th ed rules may be the biggest penalty, and there is certainly a case for getting rid of the rough riders.

But Feudal knights charging tyranids/space marines would be the ultimate act of heroic bravery.

The sentinel moves forward before the start of the first turn. At the start of the first turn, I can move it again with an act of faith – possibly putting it close enough to charging something on the enemy flank.

At the end of the first turn the rough riders get placed within 6” of a battlefield edge. I think that means that they get to shoot before they charge. Two plasma guns + 10 hunting lances is probably enough to kill a tactical squad – and I’m optimistic that I could generally end up hitting something soft, or aid with the sentinels in causing a flank of the opponents force to collapse.

Elites:

Heavy support
Autocannon team 45 pts
Mortar team 48 pts
Wyvern 113pts

I could convert the autocannons to sit on old fashioned two wheeled gun carriages, and possibly have teams of pack horses on the battlefield (essentially as scenery) that would complete the look.
If memory serves there is an old empire mortar team kit I could use with minimal conversion.

The wyvern is one of the things in this list that I find the least cool. I would much rather include a Leman russ with sponsons- but I am already behind on points. There is a certainly a good case for this being turned into another heavy weapon squad.

So far i haven't found the FW book that has dkok or sentinel lifters - so those things are not in the list. But it certainly would be cool to have close combat sentinels supporting the warglaive and rough riders in combat.

Imperial knight super heavy detachment 1113pts
Warglaive 157pts

I am imagining sending this forward with the sentinels on turn one to join the rough riders in collapsing a flank. You were completely right- having all the different shapes and sizes of noble war machine will make the army look interesting.

I’m not sure where I could get parts- but I think both this and the sentinels would need a lot of converting before they’d really feel noble enough.

Gallant. 372 pts
you can build this with the canis rex kit- apparently it comes with all the different arms, so I’m hoping that, that one kit can become whichever mid sized knight I end up using.

With acts of faith from the crusader this guy could move twice or end up fighting twice in combat (without using command points- which I don’t really understand but know are important); and then I think there are ways of ensuring knights always explode. So I am hoping that if this guy semi consistently kills or explodes in the midst of the enemies most expensive combat units this will put them in the awkward position of having to trudge across the board – already wounded and depleated as my Gaurdsmen shoot them to bits.

The other fun thing about this- is if this explosion is in the middle of their army – that also makes it harder to mobilise their forces to deal with the helvrin/sentinals/ rough riders on their flanks.

Valiant with 2 seigebreaker cannons 594pts
I’ve taken the cannons because I think they make the model look better. I really loved the old epic warlord models – so the idea of having something g like that in 40k is a lot of what got me thinking about this army.
I can see why everyone preferred the castellan and now goes for the crusader. This knight clearly needs to come within harms way to be effective, that probably means loosing wounds, and making the thunder coil harpoon less reliable.

However, having him walk straight into harms way- and unleash this mega weapon hopefully will make him feel truly epic and heroic on the battlefield. I’m also hoping that using the acts of faith to get him two opportunities to shoot on most turns will mean that he becomes reliable.

breaks my heart as a crusader enthusiast but they took away all acts of faith from crusaders with the recent sisters codex. Least that is my current understanding. Also, acts of faith can only ever be used on crusaders, not on any other imperial gaurd unit, or ministerium priests (you really want one if you have crusaders as he gives every model a third attack every melee in his aura bubble, AND he has the same effect on all your gaurd infantry).

Command points ARE important to the gallant. Various knightly strategems are what allow him to charge/advance/get into melee on turn 1 -- house krast, I believe, with the strategem "full tilt" and the warlord skill "landstrider" give you good odds of doing that, and speed your other knihgts of the same house forward at the same time. My good friend who plays knights has blown many a big knight up like that as a bomb in the front lines, much to the tears of his opponents who were not, usually, expecting to lose more points by defeating the knight than by ignoring it.

Again, acts of faith = GONE, and NEVER apply to knights at all, they are only applied to sisters of battle units, and the sisters of battle specifically exclude crusaders from being eligiable now. Its sadness!

The elysians and DKOK are found in thsi book.
https://wh40k.lexicanum.com/wiki/Imperial_Armour_-_Index:_Astra_Militarum

Also, there is a five pack of plasma guns intended for marine soldier use that you can order into the store from GW for like 12 bucks. This is an excellent way to beef up an imperial gaurd army with some easy firepower -- cause 10 plain imperial gaurd may be a bit lame -- but 6 special weapons guys with flamer, grenade launcher, grenade launcher, and 4 command squad guys with 4 plasma guns is a real easy conversion once you buy a few plasma guns. And viola, same 10 bodies, but its now BRISTLING with firepower!

For your army, you might consider making fewer 10 man gaurd blocks of troops and making a few more special weapons and command squads to sprinkle all over the field, or even veterans (a 50 point veteran squad can carry 3 special weapons, a pistol, a heavy flamer, AND a heavy weapon) .. its not that much more expensive than normal infantry, but its a lot more useful.

But in your specific case, you use the regular 10 man gaurd blobs as the cheap levies of the medieval look. Put a cadian sargeant in each group and maybe a catachan and a cadian infantry in the mix somewhere, and color coordinate the squad with itself, and you can call it a conscripted levy troop group even though its functionally just 10 gaurd regulars with 10 lasguns. It will LOOK like medieval rabble, though, albeit with the leadership and a few regulars in it. (if you ever do run pure conscripts, I would omit that bit of leadership and cadre troop to make it look like really cheap troops, a subtle but telling difference)
Then put some special weapons squads together -- either cadian or catachan. The less elite ones might be 1 flamer and 2 grenade launcher (not shabby) and the more elite ones might be 3 meltas or something, but each pile of six will be drawn from obviously the same modern kit and look like real soldiers next to the piles of mixed medieval and other. You can make them look a bit less elite by mixing catachan and cadian stuff a bit, maybe put a medieval head or two on the bodies of a few of them. Maybe the 3 guys with lasguns look a bit oldfashioned kitted out, and the 3 with grenades look more modern. These are BS4, so not "elite" gaurd infantry yet, just better equipped, still 4 points a model base.
Then add in some elite infantry.
Do a veteran squad or two. Each gets 3 special and 1 heavy weapon and potentially a heavy flamer, too. They get made by adding special weapons to the bodies of cadian (or catacahan) infantry and viola, you have created what look like quite badass normal troops, next to the less badass special weapons squad guys and the rabble of normal gaurd. Finally make a command squad or two, they are also (per model) only ONE POINT MORE than the regular gaurd troops, but they shoot at bs 3+ instead of 4+ (just like the DKOK, command squads, scions, veterans, this side is all "elite" shooting infantry. So make them look elite, make all their kit match, make it more modern. It can still be quite varied but you are now in the realm of stuff that shoots as well as actual marines in combat, even if your troops are still quite fragile.
Then put beside it some dkok stormtroopers (scion soldiers with a mix of lasguns, grenade launchers, plasma, meltas, and the sarge can use a plasma rifle) as very elite armored infantry, and put some actual scions beside that (even MORE elite armored infantry).

I bet you will fiddle around iwth exactly what you want for a long time -- and if I were you, I would use unpainted rabble as the 10 man imperial gaurd squads right now to start with an army like (cause I suspect you probably HAVE some on hand, from prior play)

1 company commander
1 yarrick
1 psyker primaris (a few psykers is good)

1 astropath
1 ministerium priest

6 x 10 man imperial gaurd regulars .. made by splitting out a pack of a couple stormtrooper cadian 10 man squads into about 50 existing medieval armor guys. Sure, its a proxy army for now, but you can play around with exact composition for later.

That gets you started. Its got 64 bodies, not too shabby, and its a tiny wedge of 466 points. As you then begin adding in the more elite infantry groups of SWS, 'eavy weap squads, veterans, dkok commando stormtroopers, scions, command squads, you can get all kinds of fancy (and you can backfill a few plasma into the rabble and a few autocannon or such, later) You may ultimately end up with something like

3 x 10 gaurd with 3 grenade launcher and 3 missle launcher and 3 laspistol and 3 chainsword (the rabble 30)
2 x 10 veteran gaurd with
....3 grenade launcher and a heavy bolter (range support)
....3 meltagun and a heavy flamer and a plasma pistol and a powersword (close up combat unit)
special weapon squad with flamer and 2 plasma rifles (hell, its cheaper to put plasma in the lower bs unit, and this isn't a "screamingly threatening" target for the enemy, so it may survive a while)
....command squad with 2 plasma and a lascannon.
scion 5 man basic troop choice
scion 5 man basic troop choice with 2 plasma and plasma pistol

Its a bigger army and now its suddenly got a feel of all sorts of different types of troops -- think of the siege of jerusalem in medieval times, the crusaders from different cities each had different speciality troop types they contributed (I think the venicians were siege warfare engine specialists, for example). So its quite reasonable with your army of a coat of many colors to add in 3 heavy weapons squads of heavy bolters later, and say "those guys are a different house that does anti-infantry fire support" or 3 guys with mortars instead and say "THOSE guys do anti-infantry siege warfare, instead of open field battle support." etc etc etc.

I think your army project is really cool -- but from a practical perspective, you might want to consider plotting out how to 1) get it table ready even if not perfect NOW rather than in two yuears and 2) get to playing and see how the cp and strategems and other tricks work. This will greatly influence your units that you keep or get rid of, as you evolve a playstyle that works with knights, gaurd infantry, and the current game ruleset and meta.

Note that with 9e, there will be some CP penalties for having more than one detachment and perhaps for mixing factions. Your current idea might not work as well with the new ruleset.