-2 BS to hit Flyers. -1 isn't enough, it really is supposed to be harder. I just always disliked that it was even across the board for ORks, eldar, marines, humans. Seemed weird.
I like buildings, we just need more complete rules for them, GW totally half-assed it. You need Look Out Sir! if you're going to have wound allocation work at all the way it does.
Yes, challenges are useless, let's ditch them. Some armies have rules specifically FOR challenges, but that those rules are mostly useless too.
Yes, 2+ saves of any kind that can be rerolled is stupid. I'd be ok if we only limited it to invo saves, though.
No, no, don't have assault ranges be 3d6, that'd be crazy. But if you wanted assault to be more prevalent, maybe let you take overwatch casualties from the back?