There actually isn't too much about the unsprung sections of a car that would be changed doing the emotor per wheel thing... there is a company out there that makes kits for Minis already.
IIRC, they have kits that have the same HP as the ICE engine does PER WHEEL, thus making your Mini a 600HP monster with no lagtime waiting for torque to build up or a turbo to spool.
Nicest thing I've ever found about E-Motors is that their torque rating is at 0 RPM. They don't need to be spun up to have torque, since they aren't fuel based. The electrical current can be just as strong at 1rpm as it is at 1200 rpm.
It'd be great to have torque on demand.
Linky:
Electric Mini: 0-60 in 4 Seconds: It Has Motors In Its Wheels : TreeHugger
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