Well, the way I would do it is have weapons in three categories [which already exist]
Light, Medium and Heavy. {pistol, basic & heavy}
Light and Pistols would require 1 action point Per hit.
Medium & Basic would require 2 action points per hit.
Heavy would require 3 action points per hit. [so you can move and attack with it.]
Light melee weapons would get reliable, and heavy melee weapons would get unreliable. These, on melee weapons, would grant fatigue on a jam.
And then I would use all of the armory from all of the previous games as is, replacing the old dark heresy with Only war, as I believe all of the weapons in that core-book are in the other one [but updated].
Alternate ranks that grant special abilities or talents would become elite advances which would grant cheaper access to talents and some specialities.
And... I would use Psychic powers from Original DH, as I've always prefered that system and they are a lot more diverse. But, likely with the tables from the Beta, with some consideration to the sorcerer which would add more on that table.
Thats juts off the top of my head