And as long as your 750w rated in a different zone motor rated 250w in the eu/uk is capped out at 15.5 mph thats cool, just as if an Aston Martin owner remains under the 70 mph speed limit on the motorway who cares his flash dick extension has the capacity for more speed...
Regardless of how much cash you throw at the machine as long as you remain within the regs re motor rating, speed limit, and pedal assistance, carry on..
The use of motor rating in the regs provides the latitude to ride machines capable of handling 99% of the terrain folk live in while with the speed cap and assistance requirement ensure that silly death cycles remain off the rd ( as long as regs are adhered to).