How about "press and hold knob" until it switches (beyond the menu..)?

I would like that very much.

It's possible that this might be what they decide to implement for the final 2.0 release anyway, so you could eventually just hijack the long press, then send a long press underneath your menu, and that would solve your mode-detection problem.

I wonder, though, if there isn't a way to detect whether tuner/aux is active from within the kernel. Perhaps by reading from the DSP?