Our team always builds fully-modular drive trains so that if anything fails spectacularly, we can have it entirely apart, replaced, and put back together in a short timeframe.
We have a bot with Rhino Treads this year and we didn't change our drive train plan at all. We still have two fully-modular drive pods so that if we break a belt, it comes apart, is replaced, and goes back onto the robot with ease.
You can see the insides of one drive pod in a picture
here.