I like the idea of a "Hybrid" system which uses the electric motor on take off to assist the (smaller?) engine. Loads of torque. No need to carry heaps of stored energy just for a take off/go around.
The real aviation benefit would be the redundancy offered by the electric motor should the engine fail in flight, sure would be nice to be able to maintain airborne for even 15 minutes to make a precautionary landing rather than a forced one!
With some clever technology might it even be possible to let the descent phase recharge the battery a bit? A bit like regenerative braking?
It would be a start, and i believe in starts!