I think the problem with normal consumers and LiPo only really exists when dealing with packs larger (in series) than common chargers can handle.
Providing that some LVC (cell level) is used to provide a cutout system - I can't forsee people having any other issues when working with 5-8S packs and chargers designed for them.
Eventually someone will brainchild on selling housings with mounts and space to accept perhaps 4x6S packs with plugs in the housing to handle parallel and all the other needed connections.. No batteries but with physical housing, HVC/LVC (or some variation of them) and appropriate plug and play connectors.
A question - what motor would you suggest to use with your drive system to acheive the absolute best high end speeds ? You know me - I'm usually a 35-40mph rider and for one I could care aless about the specifics of the law for my own builds - I only do compliance when building for customers (unless requested to do an "OFFROAD" build - ha yea off road)... in either case I have many outrunners here now but would like to pickup what you believe would be the best performing mate for your drive system.
To clarify - I will be attempting to make the system adaptable for 2 bikes at once, the complicated part 1 is 26" and one is 20" - Assuming a motor can handle a wide enough range of voltage input - I suppose 8S on a 20 and 6/5S on a 26 would about match the speeds...
Really can't wait to see these brother - been chomping at the bit for something new and I think I have quite a few customers here in my locale who will find your drive prefferable to hubs and other methods - there are quite a few spandex warriers here with the 3-4k practice bikes (you should see the race bikes) and a system like yours won't hinder changing the tires, add much weight, etc... but it could with a fairly reasonable weight provide power for the return portion of their training runs. I'm only hoping you can produce them fast enough after the first batch goes out!
TBPH: I would prefer a multi stage reduction personally but for avg Joe - I think the utter simplicity and lack of real technical challenges to installation will bring you a very nice market segment