I use a lot of MIDI piano tracks, and I would love to be able to play freely (i.e. without strictly following the metronome) and then go back and adjust the tempo map to fit the MIDI track I laid down so that future tracks can follow the flow of the piano track. It's not hard to do this with an audio track -- we have the "Don't follow" feature that decouples the audio from the tempo map. But there's no way to do this with MIDI. Of course, I can convert the MIDI to audio, but then I lose the ability to edit the notes.