I’m also very interested on MPE layers. Especially for Pure Data (a layer like the mod layer, with all channels in/out) and Surge.
To be more precise, I’m working on a digital orchestra project. We planned to setup all the things this month. For this purpose, we have some MPE interfaces, like seaboard, linnstrument, soundplane, continuumini, etc.
But I’m also creating kind of « fake MPE interfaces » by aggregating several monophonic interfaces (like Aerophones) with iConnectivity midi interfaces. In this setup, all the instruments (around 25) are in the midi network and goes to 10 headless raspberries (so, one raspi for 1 to 4 instruments, each one a specific midi channel, excepting real MPE interfaces).
And there’s also a conductor that is going to control all the raspi with program changes, specific and global panic, off, etc. (probably via an ipad and mobmuplat). So the wonderful work that you did with Zynthian (we already own a Zynthian V2 kit) seems perfect for that.
For all this, we are going to use Pure Data to precisely filter, scale and map the data (mostly thanks to the pure mapping library which is really powerful).
So, the possibility to have multi midi channels in/out in Pure Data (and Surge) should be really great for us 
And of course I’m on for testing if it’s necessary ^^
@Pastitas I’m interested on your custom layout for lightpad as we have four of them (especially for automatically changing settings by MIDI via presets embedded in Pure Data). I also had to test the freeboard blocks firmware in this sens.
Lots of work in perspective for this new year 