But nothing is preventing you from building your concept.
How many times should I say it
has been built and proven far superior than the CVT system over two years ago.
But I understand not having confidence in your bike frame for going faster than 20. In kit form, the choice of frame is wide open.
After an hour ride, the shimano is lukewarm. The CVT could cook an egg. All that heat translates to lost power. Its no contest. The idea that putting the jack-shaft in between the wheel and the 5-to1 tranny would be complicated is laughable. Nexus owns the CVT in relabililty, top speed, and plain ole' coolness.
Its just you are so close to integrating the system. Heck you could make the CVT or IGH (internal geared hub) an option.
I still think your setup is sweet. It would be about 10 dollars worth of aluminum and fasteners to add in the shifter. Move the engine to the right .75 inches...
Shifters rule!
PS your 1.5 hp must already be breaking the law. Rock on!