Sounds like it will work in theory mate... may have to be carefull with switch over points to ensure the switch takes place prior to any large inlet depression otherwise you are likely to have a very sudden and high overspeed condition on the turbos compressor / turbine.

There are some exhaust bypass valves knocking about that may be worth some investigation as an easy fit solution... yanks use them to bypass silencers electrically, wanted to fit one to the M5 but no damn room.

Additionally I would be interested to see if you could find a way to maintain some supercharger input into the compressor at all times to keep the efficiency high... that however, is likely to be a total mindfuck of a convertion requiring complex one way sealed valves, and the more I think about it, the less interested I would be in trying to do it. LOL