A cool alternative idea is to not use MIDI at all but to go for cheap
USB computer keyboards that you modify into "pedals". I
have you experimented with using the keys on your keyboard to record loops? I suspect the timing won't be as tight as via MIDI. keyboard scan rates are not designed for high-precision.
on a somewhat-related note, the old MOTU 828 that i use has a punch-in jack that you can put a footswitch into. i tried this, but found that it did not trigger things quickly enough to be a loop controller.