It's a great idea, especially if you can replace the starter motor and alternator with it. It'd be really nice to get an extra 20hp on climbout through using a cruise prop and having a little electric boost, followed by regenerating that power off the motor later. If you could tune it for the amount of drag that you got at Vbg, it could be a great safety feature.
(Also, you can put the batteries in the tail or wherever you need to to correct CoG problems. What would be fantastic, if you could get the wiring right, would be a battery you could slide along the rear fuse and get CoG near optimal every flight.)