I don’t remember where I saw it, so it could be apocryphal, but I saw an admission from an Ableton developer that the difficulty in implementing MPE support is down to the fact that MIDI implementation details are baked into a bunch of disparate components across levels of abstraction within Live, which seems pretty plausible to me. I don’t envy the effort involved in rectifying that, but it does have me looking at Bitwig more and more.