Would a wireless volume knob for home theaters be worth it?

Would it be worth it to you that is all that matter.

No, a knob would not be worth it. One of those big handles like in an airplane cockpit, that's the way to go.

I cannot imagine big knob on my remote control, so perhaps either small knob or a slider.  Buttons on my remote have just right authority/speed and anything else would be just strange (unnecessary).  On the other hand I enjoy knob on my DAC/Preamp and I wouldn't like buttons instead.