I
think you're trying to solve a non-issue
The pump itself won't draw any power if the car is shutoff , as long as the car is running the alternator will provide enough power.
If you're concerned about power usage you better not turn the radio, headlights, seat heater/ventilation etc on either
As a side note pulling the plug/fuse will log a fault and will be reported to the BMW diagnostic system if your car is at the dealer. Which in turn will likely have the side effect of them "fixing" it.