Ok, I think I get it. This helped too and some googling on variators:
Just thinking out loud,
1. Maybe a longer belt with a spring loaded, lever controlled, idler pully on the bottom? So that you squeeze the lever and it adds a bunch of slack to the belt that the pulleys can't take up completely?
2. integrate a freewheel into the outside of the clutch housing? (bearing on the outside makes it tough).