well, a functional supercharger uses 20+% of engine power, so you need an electric motor with 20% of your stock horsepower rating driving your impeller to necessitate boost management, unless you have it driving a non positive displacement pump (ie.fan), in which case the lower efficiency will require an even larger motor. Weigh the 50KW alternator (probalbly a marine part, but maybe one from a semi or bus will do), and a 30 HP electric motor, add it together, and calculate how much boost you need to compensate for the weight, then consider how much you have saved by not buying the gear, and the weight you have shaved off your brick by not installing it, and you will be way ahead.

Consider this:
WHY WOULD YOU WANT BOOST AT IDLE?