Interesting design, it might work for some games, but not for others.
We built a cantilevered dead axle drivetrain on our 2008 robot, using 1/2" threaded rod for the axles, and 1/8" thick 1x4" pultruded fiberglass for the frame members. We had an adjustable chain tensioner instead of slotted holes. It worked fine for the Overdrive game, since the playing field was flat and most of the action was driving laps.
http://www.chiefdelphi.com/media/photos/29697