[Blue Bomber Man]

A generator and a motor are essentially the same thing being used in different modes. It is possible to design a motor that works as regenerative breaking (BluWaves wheel hub motors do this).

Working with capacitors is much easier than working with batteries from I understand so far (batteries, especially li-ion and li-poly, need complicated battery management systems). The limitation of the capacitor is your gravimetric and/or volumetric density compared to batteries, and the cost. However some are working on a battery pack that is a hybrid itself: both batteries and capacitors. The capicitors serve as a buffer to the battery: they can take the high regen charge and then feed the batteries at reasonable rate, and can provide higher power when needed for acceleration. I dont know how difficult it would be to interface capacitors with a battery back that would be effecient. I do recall seeing an electric car website that someone built maybe 5-8 years ago that had a hybrid pack though. I think it is easy enough to find info on.