With the reboot, there's a lot of discussion about what to keep. Most seem to be in favor of the new character creation system, with the multiple stages, though with some revision so as not to make characters so similar.
I like that system quite a lot, but I see within it a chance to fix one of my most niggling issues with Dark Heresy: "why were you recruited?"
As presented, DH had your cell as little more than a group of bumbling rookies in their fields working for the most secret organization in the Imperium of Man, for what seemed like very little reason. This was somewhat fixed with Background Packages, but I believe such a thing should be incorporated into character creation.
This is not to boost the power level, but simply give explanation. You would still be a lowly Administratum scribe or a rookie to the Guard, but you would be the scribe that stumbled across some critical error in the manifestos - one of a cult siphoning off war materiel - or the only recruit in your squad to have survived a massacre that really should've killed you.