if you used the midibox project at http://www.ucapps.de/midibox64.html
your image would only just not work, though if you got rid of a few buttons it would, plus you could have a few faders and etc, to control effects and speed and that. which is one plus it has over the one at http://www.piengineering.com/custom/xkmatrix.php
in these upcoming holidays (late nov) im gonna have a go at building some midi stuff. i realy like your design, i think mine will be similar to yours.