It could work, like except for ladders, with the presence of the Ogryn a Horse wouldn’t be too big…
But at the very least, maybe getting the Hunting Lance as a melee weapon (Maybe with variants for the different tips ? Or having it as Krak but blessing making it possible to have another one) with an ammo System.
For the additional archetypes they need to be able to clear a few things (At least without a big change to the narrative, the systems or bringing lore contravariances):
- Would be present in the Imperial Penal System
- Not important enough that they would be kept elsewhere
- Able to introduce new things
- Has personal growth potential “As Tertium fall, Reject rises”
- Be able to do the events (Auspex)
So for example:
Ratling Can be in the Penal system, can use the Auspex, can grow, while it can introduce new weapons and abilities, those could also be brought by the Veterans, this would also involve introducing a new PoV, which cause problems due to the cover system (Before anyone say Bardin, VT2 doesn’t have a cover system)
Assassin, Rogue Trader and Xenos wouldn’t be found in the Imperial Penal system. OA would destroy the Assassin before sending them to it, Rogue Trader are protected and would only be executed by a rather foolish Inquisitor, while Xenos if they are kept as prisoner either are kept in special systems or kept for informations.
Human turned to the Tau wouldn’t really bring anything new without the introduction of a new weapon source (Which would be very strange in the presence of both Inquisitors and an Admech Tech Priest.
For possible archetypes, it’s very much Tech Adept that would be able to introduce new things, while not causing too many head aches to make it work lorewise.
Then it’s Ratling (But not Squats), something inspired by the Sister of Battle (As Zealot is already there, it could be taken up by them, but one could be introduced on the Act of Faith mechanics they have on the TT)