here's a little more "outside of the box thinking"........
MBZ uses a supercharger on their V8 models that is a "on demand" design.
an electric clutch on the pulley engages the drive belt. over at benzworld, there is a consensus the pulley/belt combo is good to 8psi. some have pushed to 15 psi. what makes them unique is the bypass valve that closes off the intake air and putting the flow through the supercharger. so....if we can get this idea to work in reverse ie. to work on the low end until the turbo lights off and then takes over. air valve opens and the electric clutch disengages. no parasitic drag and no air velocity loss....bonus
for the curious, the stock S55 MBZ SL with and without the supercharger engaged is like hyperdrive or not. on a 7* to 10* grade onramp, my CCdually is hitting 60 mph and the S55 was past 120 mph at the same reference point when I flattened the throttle. here's some pics to stir the pot.
one more thing...yes there is nothing cheap about this idea. but if your goal is to work around the design inefficiencies of a blower/turbo combo, this will put it within reach just one step closer.