Metromizer, we're on the same page... i obsess about this stuff daily
Christ, that's an EXCELLENT point about the brakes!! Rotors may not weigh much but calipers certainly do! Plus, your are replacing the hub(heavy) and axel(not too heavy).
I know that in ontario, and likely the rest of north america, a car must have two braking systems (i'm sure there are exceptions). There is no specification of what they must be, or how many wheels they must control. So you can have your regen brakes on the back and your ebrake on the front... although the opposite would be safer, but then you get into steering your drive hubs.