For the modes that use pitch detection, having MIDI out send note on/off would be a wonderful addition.
The possibilities of options in implementation might be a little daunting I'd imagine,
mostly with when NoteOff commands would be sent.
Some sort of MIDI note input would be nice. you could play a chord on a keyboard to set Learn Mode.
Or…in Diatonic or Quadravox modes, a MIDI note on would set the interval in round-robin fashion,
note off might optionally set pitch to unison mode or mute the level completely.
Just an idea, difficult to implement I know.