Just to make it clear, my comment about autorotation was with the assumption that the generator would then be dead, and putting enough heavy and possibly explosive batteries in a helicopter to have that as a backup doesn't seem remotely realistic to me. I didn't think of that the gearbox could drive the generator, which I realize now would be the only sensible thing to do.
The autorotation comment was just meant as an example of new problems that would arise with such a "hybrid" system. I still think the main points are that I can't imagine that such a system as a total would be as reliable as a driveshaft and a gearbox, and that it would be much less efficient. I could be wrong, but I still have a hard time seriously thinking of electrifying the TR to reduce the risk of failure.