I feel like it should be feasible to add a motor that gives tactile feedback by resisting turning by a little bit (e.g. for discrete power/volume level values within the allowed range) or a lotta bit (e.g. for the boundaries of said range).
Re: multi-functional sliders, I do know that motorized sliders exist in the pro audio space (e.g. to be able to program presets on mixers and such); shouldn't be too hard to adapt them to multiple functions (probably with some sort of indicator on or adjacent to the slider to show the function being manipulated).
Just FYI what you’ve described is exactly what the GPs video shows. I only mention it cause that knob and video are absolutely amazing and deserves a watch.
Re: multi-functional sliders, I do know that motorized sliders exist in the pro audio space (e.g. to be able to program presets on mixers and such); shouldn't be too hard to adapt them to multiple functions (probably with some sort of indicator on or adjacent to the slider to show the function being manipulated).