Isn't only one wheel (on each foot) powered anyway? (I can't remember) Which would mean that if you equiped another regalia it would be no diferent than a normal wheel.
Of course thats not considering the fact that it is powered by such a small battery. Creating massive amounts of energy, traveling at ridiculous speeds and generating enough friction and heeat to create fire. And thats before we get on to RAMjets and where the hell he stores the collosal amount of fuel needed to power it. There is also all the injuries, the physical stresses and strains and the remarkable anatomic powers possesed by the characters (Buccha and Om?).
Physics and Biology both weep.