I believe that once you put a vehicle on an aframe its then classed as a trailer. A Qubo will be over the max weight for an unbraked trailer. Also you would need to look at the towing capacity of the towing vehicle. If it is only for a short journey then you would probably be ok... But from what Ive read about towing I would've said that it's probably a no to being totally legal.
However, there is a big chance that I'm wrong about this!!