I like the idea, and you could practice most places without worrying about noise. Certainly seem more than capable for the average club rider, must be strange with no engine breaking. Of course we have a whole generation of youngsters learning on Oset and Mecatecno elec bikes at the moment.
Apart from a possible weight penalty there is no reason not to have regenerative braking from the electric motor. Our electric fork lift trucks have this and lifting off the go pedal has the same effect as standing on the brakes. Very effectively stopping around 2 tonnes of truck and a ton of cargo on a pallet.