2 speed Supercharger
 

Not cheap but still interesting. It's been done in the past with dual belts but never with an internal transmission. Now if we can just get Richard to add a transmission to the axial flow!

http://www.fastcar.co.uk/New_superch...nJoa2rmWw.html

I believe two speed gearbox driven superchargers were common in aero engines during WW2.

Also, a gearbox driven blower is impractical during cruise. Lots of friction to kill the efficiency. I guess you could add an electromagnetic clutch to the assembly. Now we are talking about a blower that costs as much as an engine.

That two speed (£4,000) is already more costly than the entire renesis. :/

I still think a CVT would be the best way to do it. If you're going to do it, do it right. :)

If it was electrically driven, you'd have even more flexibility, no parasitic loss, less complexity and the possibility to recycle braking energy but you need an extra set of batteries, which however can be placed such that the center of gravity is lowered as well as the yaw moment of the vehicle.
http://www.turbodriven.com/files/new...er_115_121.pdf (page 8)