Jake Jacoby ran a banked cloverleaf track at PREZCON earlier this year. It was possible to have chariots crossing the center from 2 directions at the same time. You were not allowed to "back track" or anything like that though - you had to race in the direction of the finish line. That particular track seemed to favor light chariots quite a bit; or at least faster chariots quite a bit.
That sounds exactly like what I was thinking about. You know if there's any pictures of that board around anywhere?
After playing my first game today I feel slightly more qualified to say that different boards would be cool, but not at all needed. The distances are actually balanced out quite well.