In theory it is simple to do. My version would be to engineer a turbocharger with gears in it to attach a pulley to it with an over-run clutch. When gunned, the engine will near-instantly spool the turbo up (providing instant boost) and then the exhaust will take over, taking the load off the engine AND providing more boost.
BUT a few problems:
1. Engineering a gearbox for the turbo that can handle the load AND the incredibly high rpms that the turbo will be operating at.
2. Once or IF designed, the components will not be cheap to manufacture
3. If its not around now then the VERY smart engineers at any car company (except ford
) must know exactly why that is because if a 15 year old kid can come up with a concept like this one on his own (how old I was when I thought of it) then it has definately crossed a few other minds as well.