I've also played with the idea of running something like the probox (with added features in the future) on a rasperry pi. I'm no programmer, but I started working on it anyway
I ended up soldering a usb-serial cabel, bought very cheap on ebay, to the mainboard, so I was more hardware independed in regards to the OS. I then set out to program the thing in JUCE (c++ library), since it's seemed very accessible, and has a great many elements making this whole thing easier.
However, my knowledge of the system calls to the console is limited to what I could find thru this forum. For example I have no idea how to speed up the communication with the console in the firmware. Knowing all the details of the firmware would make programming this thing much easier
I came to the point of ironing out the details in the communication with the daw software, and my next step would be to make the whole controller setup user asignable.
However, my relationship with the mother of my son went south, and this has been eating my time and money for the past year :-/
I have a spare cpu (and live in europe). However, the power plug of my main cpu is not connecting too firmly to the console, so sometimes I get a flashing and clicking console when booting. Usually it is fixable by jerking the power plug around, but it doesn't seem like the most stable solution
I'm thinking about replacing the power cable with the one from the older cpu.....