cyberham you have Princess Auto stores in the far east? Cool! Scary place to browse through... I never leave empty-handed!
Should be able to add a magnet wheel and switch. The really short one ould be nice for declination if it had a sensor.
Good catch. Yes that might be a problem with a 24v -36v controller! Could use really thin wiring to create voltage drop... but that would make for some hot wiring... maybe mod the controller output would be safer.