Ours looks a lot like that, actually.
Simple box frame with a Mecanum drive, 'forklift' arm, standard bumpers. (no minibot, though.)
We actually have a pretty cool idea for the bumper attachment that you may like:
The bumpers have inch long brackets similar in shape to sections of C-channel attacked to them with holes aligned with the C-channel itself, and the two are connected by running a pin through the bracket and C-channel. The pin is a quarter-inch wide, 2-inch long metal rod with a pull ring at one end and a spring loaded ball on the other end that causes it to stay in the hole when inserted. To remove the bumpers, you simply pull the rings.
We found this when messing around with one of the pins and a piece of C-channel in our mentor's basement last year.
