Hi Tim,
I'm in middle Tennessee, about a hour south of Nashville; work in Franklin. Since I have about a 105 mile round trip commute 3 or 4 days a week you can imagine I am sensitive to ideas to save fuel.
My idea for a powered bike is basically what I call a mid drive hybrid. Long wheel base recumbents are, in my opinion, the most comfortable bikes on the market, but they have a long drive chain that often crosses idlers that are under the seat area. My plan is to replace this idler with a pair of freewheel mounted sprokets. One of these sprockets would have a normal length chain going to a normal rear wheel cog cassette; 9 or 10 speed. Thru the action of the freewheel pawls, the sprocket connected to the rear wheel cog set can be driven by either an electric motor or by the second sprocket mounted beside it, or by both at the same time. The second sprocket is of course connected by another chain to the crank set up front. What all this means is you can pedal this bike without having to spin the motor, or you can run the motor with out spinning the crank set, or you can combine the two however you want. A control signal can even be generated by the chain tensioner from the crank set drive that will apply a proportional assist by the electric motor. This could be set to make a 70 pound bike feel like a 15 pound bike, for instance. Also, the motor will be driving throught the same derailleur as the crankset so you would have gears to optimize the output from the motor.
My final refinment to this design, and what makes it a true hybrid, is I plan to add a trailer. On the trailer I would have additional battery power as well as a small gas powered generator. This allows a bike to be designed at the lightest possible weight and have maybe 20 to 25 mile range with small light batteries and then if you have a long trip to make or a heavy load to pull up a big hill you just hook on the trailer. I think this setup could have almost unlimited range with the gas assist.