Is there perhaps already a function in BIAB equivalent to creating a UserTrack, but with MIDI? If so, could somebody clue me in?

If not, then I hereby request that as an enhancement. I'd like to be able to give BIAB a MIDI instrument track along with the chord progression for that track, and have BIAB make that available as a MIDI instrument for other progressions, just like it will for audio UserTracks. Then (obviously) I'd have the flexibility to vary the audio generated by the MIDI track, trying out different sounds, which would be a big deal.