I don't want to stop you in your project, sounds interesting. But I hacked an old Roland FC-100 mkII foot controller and I got 8 foot switches and 8 banks, sending already seted midi messages (the hack consists in changing the output cable for a midi cable). It also has some more functions. Maybe you are looking fully do it yourself, in that case ignore my advise. Good luck!
http://music-electronics-forum.com/t2932/ (Roland FC-100 hack)