[Kyle]

Make room on the cart to hold your controls so some one doesn't have to carry, and possibly drop them, also comes in handy for testing in the cart.

Try to make the cart so the wheels/treads are free so you can do a preflight check with out having to take the bot down.
Oh and the door thing is a major issues try to have at least an inch on each side for a standard door, they can vary that much in some places.
Remember that the cart might be able to fit through the door but the robot has to be on it also so make sure to measure carefully on that one.