shifting to me is the major point. i'd want gears for more than just hill climbing. i'm all about speed, yet speed in a safe way. i've got a few concepts of my own, but most of them rely on outdated ideas and obsolete products used in the past.
for instance, the Browning bicycle transmission: The Browning Automatic Bicycle Transmission
i have 2 of the 2 speed BMX ones sitting here, wondering if i could adapt one to a rear wheel sprocket.
i also have something else that's top secret till i build a test bike which is more like an actual, internal 3 speed transmission.
lack of funds is all that keeps me from building up the bikes.