Another idea that came up lately:
I used to work a lot with music trackers.
Most of them have a feature called "Glide to next note"
which pitch-bends the current note to glide to the next note. This is very very cool.
This sounds like some kind of auto-portamento, but it is not. Sounds very different,
to me much more sophisticated, especially on long notes.
If we would have an additional entry in the pitch bend drop-down menu with "glide"
this would fit quite well I think. Metro would need to calculate the distance to the next note
and adjust that by the Pitchbend range for the instrument.
Metro is already perfectly set up for that because it has a built-in manual adjustment of the pitch bend range that is used by the instrument.
Maybe worth a thought.
Best,
tL.