just for fun, come up with deathwatch alike rules and units:
HQ
cc inquisitor
ranged inquisitor
psyker inquisitor
captain
librarian
chaplain
Elites
marine adaptations of xenos races
max. five marines with upgrades from tau, eldar or necrons
Troops
tactical squad as per usual(maybe +1 attack), with camo cloak-ish stealth option, option for special issue ammo(sternguard alike) and some xenos weapon options
scouts, same idea as the above I guess, or maybe with some guard/inquisitorial henchmen feel to it
Dedicated Transports
landspeeder storm(maybe a bigger version to transport marines?)
'undercover' rhino(looted wagon/trojan horse idea)
Fast Attack
valkyrie/vendetta alike option
stormtalon-ish thing
just as in elites, some special adapted squads,
max. five marines with upgrades from tyranids, dark eldar and orks
I was thinking about something like fast attack scouts, with some jumppack equivalent, but because jumppacks aren't stealthy, they are quite the no go in deathwatch I think... help me out here
Heavy Support
Stormraven
dreadnought-sentinel crossbreed(something mecha that look like it can run and hide and stuff) with deepstrike possibility(gliders perhaps?)
and I was thinking of something with a big gun that can come on the board fast and silent - with chariot rules (how about a dogsled?)
perhaps some snipering marines(with railguns and other xenos weaponry)
then for the special rules and xenos weapons,
I'd say, per army up to three weapons of each class(pistols - assault, rapid fire - heavy, salvo)
then have some key rules per army(not worked out yet:
tau
-stealth
eldar
-fleet
dark eldar
-poison ranged
nids
-poison attacks
necrons
-reanimation protocol(regeneration)
orks
-animosity(inflict on others)
and some armor-ish specials:
tau
-stealth suits and jetpacks
eldar
-
dark eldar
-something that adds stealth?
nids
-hardened carapace(or winged rippers bound to their backpacks, that would be hilarious

)
necrons
-something that protects against necron weaponry or so(reflection shields?)
orks
-mega armor
well, this is my first look at it, I hope you like it and can help me further!
my guidelines are to start with a marines codex and give it a navy seal feel together with the xenos waeponry acces
Humey