I still think that my idea of eq-knob is the most intuitive sorry for braggin' .
It's like you press the knobb, move your finger away from the knob - while touching the screen - and then start adjusting by rotating around the knob.

Oh and about the monitoring...
I still think that using bt-headphones is the only feasible way to go.
I think that the most simple way to implement hp monitoring is to do it like it's done on pioneers djm-400:
- when neither is selected for plf, you'll hear what's going on at master out.
-when on is selected, you'll hear the selected from the left side and master from right.
-when you select both, you'll hear both irregardless of the crossfader position.