Long story short : father in law did never talk again about the project. So I went to make a midification of my old Yamaha gear (Yamaha DSR-2000) but then the keyboard fall and is broken.
Now, we are a year later and i come back to midi keyboard. A 4 octaves one. And it's working ! And right now, i see some issue... like... The screen... it take me so much time to have it working and i did see that it's useless ! haha. And I can have 4 analog input, that's great, but not more than 4. And worst, i will never have "octave up/down" button because I can't have button.
So i should go to MidiBox_NG instead of MidiBox_KB, even for a simple nude keyboard. In fact, the only -really- missing things are the octave up/down, and being able to change the USB-Midi settings. Like I would like to have only two USB ports, one dedicated for the keyboard (with midi IN and OUT 1) and the other dedicated for Midi In and Out 2.
Well. Just to say : still alive !