You are describing the function of a sc with a vacuum controled bypass valve. If you have a high vacuum in the manifold valve opens and recirculates the air. mash on the throttle (open the butterfly) low vacuum, or none, and the valve closes creating boost. - ONLY when you need it.
But it's still generating heat (and lots of it) even if it's being bypassed, or does it shut down completely? If it shuts down completely, then you'd have to wait for it to spool up, just like a turbo...