Great! I’m happy to see this topic as i just ordered my xmas gift, a Roli Blocks 
and i hope to add MPE support as soon as i can start experimenting with it. My proposal is to add a new type of “MPE layer” that would ask for the number of channels of polyphony. It would work for most of engines, except:
- setbfree
- Aeolus
- Pianoteq
It would use the already existing Master Channel for receiving the common MIDI CC messages and will resend them to the MPE channels. You could create a single MPE layer, but i don’t think this is a major limitation.
I would love to ear your opinions and suggestions …
Thanks!