As a new-ish pedal steel player, I can offer some ergonomic advices. This isn't a very popular instrument, so this may need an introduction: pedal steel is kind of like a guitar with a system of knee lever and foot pedals to modify string tension on the fly. The most used pedals are the leftmost two (in classic country), and you need to be able to select each one independently or together pretty fast.

My main takeaway:

* You usually don't use your ankle that way, so it will seems impossible at first, but you will very fast get used to "ankle rolling" which will make you able to select each pedal without moving your foot sideways

* The height of the pedal is crucial. On steel, you will have a threaded rod to set the height. You usually want (if you are using your left foot) the leftmost pedal to be around 10mm higher and with a shorter course (for both pedal to be at the same height when depressed).

* Footwear impacts your feeling, especially heel height. So if you plan to use such a device with a specific shoe, train with that specific shoe.

If you want to build such a pedal (especially a "chorded" version), I think taking cues from pedal steel hardware would be a good idea, as you need to be able to play for hours without straining your legs.