i dont think there would be a huge loss. you can freely spin a turbocharger with ur hand. i figured running the hot side of a charger through the auxilery belt to drag out the exhaust would be pretty nifty. maybe if there were some changes in design of the motor this could be useful at high rpms.
When you "freely spin a turbocharger with ur hand" you are hardly doing anything. A turbocharger does work when it's plumbed into an engine that provides a resistance. That, and when it's spinning at something like 100,000rpm...which is much more than you can hope to accomplish with your hand.
Again, you are underestimating how much brute force it can take to move air around.