Ork Monowheel Riders (to make)

I got some funny parts and want to make few monowheels to use them as nob bikers. This is (current) set per biker:


To tell the truth, I jumped the idea without real plan, how to make them. Generally, wheel has to be outside and bike frame inside ;-) with a rider but "devil sits within details", as they say in Poland.
So, feel free to help me - if other bits are needed, no problem as long as they are plastic...