Looks pretty cool.
A few comments:
1. Figure out your bumper mounting. This is something most people ignore until the "end" but the sooner you think about it the happier you'll be with the implementation.
2. I've found the 6" diameter AndyMark omni-wheels work a lot better when they're run as duallies -- you should consider that for your H-Drive implementation.
3. I believe you're sacrificing some functionality at the expense of versatility. "Jack of All Trades, Master of None." In my experience, it is very very very rare for a team to switch drive styles mid-season. As a result, it might be better for you to CAD several different configuration specific designs, knowing that you'll be able to do subtle things to make them better than this one design that does all of them. If you prioritize versatility enough that you're willing to make tradeoffs (they may be big, they may be small) then you have nothing to worry about. Your mileage may vary.
-John