Hot damn!
Just realized something ...
At 48V 10A controller this current regulated motor outputs 350w at the optimal point for 20mph USA "legal".
At 48V 20A controller this current regulated motor outputs 750w USA "legal" max motor output.
A simple PAS sensor and module could either limit controller amps or throttle signal strength.
Either, could limit a 20A = 750w motor output to 10A 350w motor output.
This could qualify as USA "legal" meeting the "20mph limit from motor only" and "750w maximum motor output".
Just turn the pedals around (No longer "motor only" = Turbo Engaged!) and hit near 30mph ... 30mph+ with just a minimal effort applied.



Your motor only speed is where Power intersects Load

"Load Line" (Black) is for a mountain Bike ... Race bike, recumbent etc., would require PAS adjustment to meet "legal".