I like the idea of electric assist, but, I also like the idea of riding under my own power on a nice light bike. Rather than dedicate a bike to electric power, how about an e trailer that, in addition to greatly increasing your cargo capacity, serves to push you up hills or help drop that pesky roadie.

Seems like it might be a good idea, especially for commuters or utility bikers.

The only potential problem I can think of would be possible handlnig issues. Would a trailer with a hitch point close to the rear wheel axle cause handling problems? I couls see how it might cause issues in turns.

I suspect this has already been done and seem to remember maybe reading about it quite a while ago, but, a quick search didn't bring anything up.

Such a trailer could also be rigged to carry passenger(s).