Awesome job! Even if you never build this, you'll have learned a lot!
My Opinion on Crab:
Crab will only offer an advantage when you must maintain a specific angle of orientation with the game piece or goal. Crab will NOT offer any major advantage when the game pieces can be picked up from any angle, and/or the goal can be accessed from any angle. A good example of this is 2008. The balls were round... It didn't matter what angle you approached them from (same for the overpass). There was no need to go sideways, you could just turn and approach them from a different angle. As a result robots that used crab were almost exactly as successful as robots that didn't. Of course this is all just my own opinion, take it or leave it.
On another note...
I was recently researching a battlebot when I found something very cool which yall might be interested in seeing.
If I didn't know better I'd say they built this for FIRST. (click 'robots,' and then 'Mechanical Maniac'). Its certainly a very innovative Crab design - uses no gears and looks like it might be easy to build.
Check it out! They are using some neat bearings you might want to incorporate into your swerve design.