So, the next version is being built :-)
The first one was great, but my setup would suit more buttons and inputs than the first allowed.
The new plan is to use a Pisound soundcard on a Pi4 4gb, and to create a midi controller separately in a modular build in a small pedalboard.
So far the Pisound has been acquired, as has some Arduino midi bits and bobs to try some plans out.
My IO needs need to be thought out fully, but so far I know I need:
Minimum 5 footswitches - for controlling 5 effects.
2-3 encoders per footswitch - to assign parameters to.
2 footswitches for cycling up and down patches.
I2c display for information (I'm feeling a Nextion display)
Two tea jack sockets for expression pedal inputs.
The Pisound has MIDI ports on it so I could use either a midi shield on a normal Arduino, or use a Due/Leonardo/Pro Micro w/expander for a native USB MIDI input.
Enclosure plans are still up in the air; I have a standalone case for the Pi and Pisound, and I'm split between going for a large enclosure to house them all, a medium enclosure for just the MIDI controller, or a few small stompox pedal boxes daisychained together to look like an old school pedalboard.
Either way, this is going to be fun!