This reply doesn't really answer your question/s. But I will say this...
When I was trying to figure out how to make a rotary controller / 'Discs of TRON Spinner' - I also envisioned being able to connect some handle controls to it or a steering wheel, which would connect to the knob that rotates. I'd also need a way to lock it from moving up/down, as well as add some tension and limits to how far it could turn -if needed.