That second idea looks promising. It'd be a nice 'boost' engine, but it looks too small to provide sole power for the car. If it could do 20 miles form 0-25 I'd be interested, but the weight has to be a liability. Although the weight is nicely distributed, I'll bet that's 300 pounds. That would take the edge off our little Bimmers, wouldn't it?
It's also a 'mild hybrid' conversion. No way to recharge other than a home setup.
As for the electronic supercharger, they're garbage. I did see a legitimate one, but it required a really solid ~2hp DC motor, gearbox and half a turbocharger impeller. Worked well up to 6psi but was very cumbersome, requiring substantial electrical upgrades to the vehicle's charging system.