[Al Skierkiewicz]

OK, Ryan,
Here is some answers for you. Electrical slip rings are legal if you can follow the flow chart, (commercial ones can) if they can handle the current (you need to prove it to an inspector), they meet the max cost limit, and if they do not conduct current to the frame (most do not). I have seen a team who pulled apart a light reel (the kind you see in garages that hang from the ceiling) and used the innards. You need to account for the cost of the reel in BOM, I think it is about $100.
On to your other issues. You will find anyone who does crab effectively (we have done it for several years but not this year) will not use bevel gears for drive. There are two problems, they are inefficient and they need substantial bearing surfaces to keep them in alignment. Remember that as the wheels turn, the engagement also moves. If you are not dead nuts on in alignment, your frictional losses change as you turn. Those losses translate into speed changes that make things very hard for the driver.
Crab drives require some software massaging to make things easy for the driver, that interpret where you are and where the driver wants to go. Although it looks good on paper, continuous rotation brings some other problems to bear like feedback from the steering. If you use a continuous pot, you have to compensate for when the pot goes from max resistance to min resistance in a fraction of a revolution. If you use a rotary encoder, you need to know where your steering is when the robot wakes up or set it to some fixed point during initialization. (You can't know where you are going till you know where you have been) All of these obstacles are surmountable though and many teams have come up with their own twist. Check out Beatty or HOT at nationals for two teams off the top of my head that are using crab.
The last thing to consider, crab drive, although very flexible (sort of like point and shoot cameras) cannot turn to change attitude. This is a must in a game like this year where the goals are angled to your direction of travel. You can drop into a tank style drive in software, but run into the high friction those kinds of turns demand. Or what some teams do, is drop a low friction foot, pneumatically, to raise two wheels off the floor, set the robot into a tank style turn and then retract the foot when the desired attitude is achieved. HOT uses a three wheel crab where the third wheel appears to steer independently. I didn't get a chance to look closely at WMR but it looked good on the field and I could see two Chalupas on the back drives.