Cool. I'm happy to help with specifics when you get to those decisions. Regarding control inputs, pi-Stomp offers 8 ADC and 5 debounce. You can use some of the ADC ins if you need more footswitches, but you might need to do some minor code tweaks. There are 3 undedicated GPIO's, 5 if you don't add serial MIDI (USB midi is always available without using up any GPIOs). I assume you are planning to have an LCD, right?