[meej]

> Makes me wonder if you could make an electric-assist bike where the assist was on the front wheel, thus saving all the complicated mechanical power transfer.

This exists, it's called the GeoOrbital Wheel. It converts your bike to electric just by swapping out the front wheel. Pedaling is optional, so it's actually more than just an assist, it can operate in a fully electric mode. http://www.geoo.com

I own one and I'm very pleased with it.

There are also a bunch of front wheel e-bike conversion kits on Amazon, last I looked.