That's actually really cool! I have put in some work to write a BLM proxy that runs headless on a Raspberry PI -> https://github.com/westlicht/midibox-blm-proxy
Unfortunately, while working perfectly fine on my Linux workstation, I had some sporadic lag issues when running it on a PI.
One problem I see with your approach is, that it will be difficult to handle more than one Launchpad, right? The USB host on MIOS does not yet support HUBs if I remember correctly. My goal was to have too Launchpad Minis to get a larger grid, which is quite cool for programming drums. I should really pick this up again and make this work with the PI. Wanted to check out if I can get rid of the lags when using some soft-realtime kernel.
Because I have started building a DIY modular synth over the past few months, my time is kinda drained by that :)