no suggestions except that sounds absolutely awesome. I could totally see a numpad with some toggle switches to set various layers.

Edit: I would put this switch on there: https://www.sparkfun.com/products/11310

The Ergodox supports (Infinity in this case) UART protocol over the USB 3.0 pins for "daisy chaining other Infinity devices such as number pads, mice, other keyboards, etc."

I'd like to add a pair of 3 switch foot pedals and use them for things like lock and latch either by modifying my existing pedals or creating an adapter that would take the programable HID output from the pedal and pass it on in UART to the Ergodox. Anyone seen something like this or have any suggestions?

Ergodox UART extension