In my experience, cooling is going to be your biggest hurdle. On my air cooled sr185 I used a combination of cooling fans and oil cooler to solve this problem. ducting enough air to cool your bike will only work at speed, since in city traffic not enough air will be forced through. I know this from experience. This year I hope to go 100% fan cooled, eliminating the ducts.
as for motors for a hybrid setup, you could look at what they have at
Electric Motorsport They are set up specifically for motorcycles and such. I've been eyeing their brushless setups for some time now, but can't afford one yet.