This might not be the right place or the right time to post this but here we go. This is what I'd want, and I'm not paying 20 bucks to see what's in there.
Rogue trader style character creation, preferably fleshed out (think burning wheel)
Un-combined skills: Stealth was better when it was 2 skills, search was better when it was not just awareness
Mechanics brought back closer to old dark heresy ie more cthulhu in space, less Eisonhorn's awesome possey(wounds being more serious and doing stuff before criticals is good, playing as an inquisitor is bad).
Combat rules being fixed, ie balance full auto and accurate, while still leaving room for using non accurate and semi auto weapons without gimping oneself (the ability to supress with semi auto was a good addition in OW)
Slightly more flexible character advancement, but not the sprawling mess that was Black Crusade. Some combination of original DH and OW would be my preference.
Throne geld remaining in the game. I like buying stuff and figuring out how to spend limited resources.
Psykers using DH system. The variable strength of using lots of d10s is much better than pushing/fettering and what not.
Looking at the char sheet, it seems mutations have been removed. This is horrible
Dems my opinions.