Interesting... Why off a seperate button and not off the steering wheel/arduino you already have ?
The EDC button should have two indicator leds. I didn't have a way of displaying this anywhere so I'm using the Z4 button's built in LED and another just below the button to indicate sport+.
Couldn't/wouldn't get an M3 console since LCI CIC + manual + RHD is beyond rare - also didn't want to bother making a switch input to the CAN module (M POWER).
I also wanted to control the dampers separately from the steering wheel button. The funny bit is that the SVT module will look at EDC status to switch assistance curves which means I'm inevitably still tying up more than one thing to that button. At least steering+dampers makes sense.