Using the --debug mode, I started to learn all the primary buttons. It's really easy : I take a printed scheme of my Kontrol DJ, push buttons under debug mode, than read the mixxx.log, and translate the info using the wiki (example : it's a ON/OFF message, and it's the 0x02 button) then note it on the printed paper scheme.
Once I've done that, I made the basic midi learning wizard. Then, I manually add (using the "add button" in the MIXX midi prefs interface) each button I noted (for buttons, it's quite simple, basically you just have to enter the correct control number : 0X"something in hexadecimal"), and it's working. No need for script or XML...for now
Well, I'll map all the basic buttons primary functions tonight, then I'll come back to you for the complex operations (shift and select buttons for secondary or even 3rd functionality, endless rotary push knobs for track selection, jog wheels).
