I'd love it if the octave buttons would change colours depending on your current octave so you can tell where you are at a glance. Upon switching instruments I usually don't know which octave best fits the new instrument, and I can't tell where I am in the octaves.
All it would take is a simple system like this:
Octave 0: both lights blank (or red)
Octave +1 : "octave up" button turns orange
Octave +2: "octave up" button lights green
and vice versa using the "octave down" button lights when descending from octave 0. This would be super handy, and who doesn't love more flashing lights?