you may not have theresources or funding to do such a thing, but Georgia Tech did, and with me and 4 of my friends this was our senior design project.

having been there, and done that may i +1 on dannihilators suggestion of belt drive with an internal gearbox.

the prject was hugely complicated, and vastly over built. it weighed a ton, and was not practical in anyway.
That being said, we did build a prototype of the drivetrain, and it did work. so maybe it will work?

all i know i the frame that was to be our prototype is now my fixie, and it is a lot more useful!!!!