Stuff I'd like to see:
d% rolls as the only resolution mechanic.
Better, clearer and more precise rules for degrees of failure and success.
A bit of skill consolidation. Particularly for stuff like sneak, conceal, shadowing, and for the various advanced group skills. Do we really need separate occult, warp, and daemonology skills?
Talents build around the concept of increasing chance of success, rather than adding new abilities and myriad forms of rules exceptions.
Fixed (non-random), location-specific damage causing cumulative penalties and armour degradation.
An end to class, toughness, armour, damage, psy and cyber power creep.
More levels of less restrictive, lower-powered jobs with fewer requisites and fewer types of requisites.
Some kind of limitation on the amount of times characters can use "powers", and a single mechanic for doing so.
Mass combat rules.
Vehicle combat rules.
Space combat rules.
Atmospheric flight combat rules.
Rules for designing all manner and sizes of units and vehicles.
Squats, Ogryns and Ratlings as playable races.
Economy based on rank, renown and contacts, rather than money.
An initial power level of 2-3 hits and you're down, but not dead, and a power curve that doesn't rise much beyond that, ever.
An end to wonky math. Pretty much nothing and no-one should ever hit more than 70 in a characteristic, and 95% in a skill check.
Starting characteristics ranging from 30-50, rather than 20-40, and characteristics should either be point buy or picked from fixed distributions. Rolling dice for this is silly.
Squad-based event resolution. Squad combat rules, and rules for problem solving as a unit.
… And piles more stuff. But I'm increasingly dissatisfied with the system, my group has already done much work on all of the above and much more, Zweihänder promises to do a lot of the above, and if all else fails we do have a back-up system we really love. So… Perhaps the only really relevant thing I have to say, is that I'd like to see is OW returned to being a DH supplement, rather than the 5th republishing of the same 300 pages in a 400 page book. Many spalts = good. More than one core = bad.