Looking closer at the LCD board there is a light controlling circuit that seems to be either "always on" or press a button for a preset period of light set by a trimpot. I figure cut a few traces, solder a few jumpers and could get control over the lighting and the button as input to RepRap firmware.
But seems that the only PWM capable pin is shared between the SERVO and Z_PROBE_IN so no dimming, and currently only end stops support triggers i.e. no dice on the switch as an input, for now. On/off would work, but no means of getting user inputs. Maybe revisit in 3.0 unless 2.04 get support for general i/o triggers first.
Filing the sketch under wishful thinking for now:
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