It's not really that simple...
If you change the definition of ebike to be a powered vehicle which you don't need to pedal that includes pretty much every vehicle on the road. So all cars are now classed as ebikes and are limited to the same power/speed restrictions?
Id like to see how far you get in a car limited to 250w.
That said if you need to change legislation it’s not that difficult to do it properly and put in a proper legal framework for them.