Is it possible to create something similar to a butterfly drive, but replace the pneumatic cylinders with gokart springs and shocks, ie:
http://www.ebay.com/itm/UNIVERSAL-SH...AOSwu4BVvEp i
or maybe simply a spring?
In this manner, the wheel changes height to cross over the defenses, but the chassis stay more or less at the same height, similar to a car.