Heres the idea: If you make an AC motor controller and hook it up to feed the three phase coils in an alternator in phase(the brown bit is an angle sensor), the IC-controller in the alternator will decrease the field coil current because it sees the increased output voltage. At some point, as you increase the fed current, the EMF in the phase coils will be lower than the voltage you feed from the AC-MC and the current will reverse, and the "output"-torque of the alt will go from negative to positive, and viola, you have a motor!
And, you are, at the same time, providing the correct output voltage for the cars electrical system! Doing the same when the alt is not spinning would have to be done with the red and blue wire. (And the purple wire might have to be used to fool the car that the alt was working)
Since we didn't remove any components, only added some, putting the controller in high output impedance mode would cause the alternator to simply revert back to being an alternator. In fact, it can be done gradually, as the output of the controller is decreased, the alt just picks up the slack.
Regen could be done by drawing current from the red and blue wire, and boosting it up to plugin pack voltage. (Did i forget to mention there was a plugin pack from which all the energy came from?)
