RE: hybrid operation

Depends on what kind of hybrid. There are multi-fuel engine conversions done, which would qualify the car as a hybrid.

I would guess it would cost more than just buying a Prius. It would take major driveline changes (adding a large electric motor, generator, etc.), adding a heavy bunch of batteries, which would require beefing up the area of the car where they are located, and developing and producing a sophisticated controller. The Prius uses a CVT, not many of them around aftermarket. Engine needs to be modified. LOTS of work, lots of design issues.

Gas to electric conversions are pretty common. Hybrid drivetrains require a more 'whole-vehicle' approach. Conversions would be unlikely.