pritty amazing stuff. - My first thought is the big drive wheel doesn't have to be at the hub, it could be driven by a short offset drive (I,m thinking ground clearance here)
and secondly, gearing, you wouldn't pull off in 5th in the car, your going to need some fancy gears to build you up to it, but once your going - your going to need bloody good brakes!! - possibily syncronised. rider position looks good.
on a lesser scale.