I saw the post about the Cherry Audio Taurus Pedals which reminded me to show the construction sequence of some DIY Bass Pedals. The pictures are in sequence and it took about six weeks working on them nights and weekends. Heart of system is a MEGA. Two expression pedals, 17 notes, and 10 other foot switches are programmable. However, once the MIDI (over DIN - USB is for programming the MEGA only) is captured by Cantabile, the MIDI filters can do almost anything. Step on a note, Cantabile converts to CC to send to a Kemper (or mixer) to engage an echo, load a patch, etc.
There was a post about DIY switches earlier this year; maybe this will spark some other ideas. Arduino to MIDI is easy to program and has been very stable.