A problem is that if the bicycle goes above 20mph, it is a scooter and would fall under motorcycling laws. That means licensing and insurance. Generally under 20 miles or so it is considered a moped and is treated differently.

Also no offense, but going 20 mph in a bike lane or worse a sidewalk would be very bad. An ebike is not a bike, but a moped under the classic definition, a bicycle with pedals and a engine to provide supplemental power. It's just not a gas moped.