Your posts are full of generalizations that are debatable at best.
I don't get your reasoning about smaller wheels being the way to maximum maneuverability. It's a combination of a lot of things, center of gravity, wheelbase, overall weight, rake and trail of the forks, etc. The most agile of all 2 wheeled vehicules, trials bikes have big wheels. The reason scooters have small wheels is to make space for the floor board. And then there is the down-side to small wheels, potholes. Are there no potholes in Shanghai?
Actually, wheel size is a moot point. The single most importatant factor in congested, free-for-all city riding is width of the handebars, the ability to squeeze between traffic and other obstacles. And here, an Ebike ould have the advantage over an Escooter.
By that as it may be, rather than reinventing the Escooter, why don't you do some legwork once you are there and find the best model available and work with that. Batteries, controllers, hub motors and wiring are all easily up-graded. Besides all the complications of engineering a belt drive/RC motor system, it would eat up space that could be used for batteries.
Besides, your sweeping comment that that Escooters are not well built is true in the sense that the sub-systems are substandard[compared to the Japanese offings]. Things like the general wiring, body panels, hardware, suspension components etc. are the weak areas. The hub motors and controllers are the most realible systems on those scooters and replacing them does nothing to address the Chinese Escooter weak points.
If you start with a scooter with a trailing-link frt. fork, you could mount a second hub motor for 2wd, which I.M.O., would make for the ultimate urban Street-Fighter Escooter.