I’d like to see Xenos included at some point seeing as we are serving an inquisitor.
I can see Arbites or Enforcer being a sub-class for the Veteran being next. Death Cultist or Redemptionist for the Zealot. Some kind of ranged Ogryn build and maybe a melee heavy psyker or psyker with access to bolt weapons.
Honestly I wish the class skills were in a larger skill pool that we could pick 6 freely from. Adding new classes adds more general traits but gives a new top line skills. Would give us an opportunity to really fine tune our character.