I actually got rid of the UNO chip and got one like the one @Neil mentioned in the original post on the basis of actually dumbing down the FCB to just a bunch of buttons that send control commands and having all the smart stuff in Cantabile.
The problem with the original ROM as well as the UNO ROM is that they are trying to be too smart with banks, program changes and stompboxes and so on. I prefer a mode that lets me simply receive a control change from every button and pedal and lets me send CCs to turn the LEDs on or off, depending on Cantabile states. No banks and programs and fancy configuration, simply a dumb controller with no internal states.
I use the Eureka Prom in simple Input / Output mode, which lets me do exactly that - I can receive CC messages from every button / pedal, and I can send out CCs to turn the LEDs on or off. Unfortunately the CC mapping to LEDs is a bit convoluted, but nothing that a bit of ReaJS programming can’t fix…
Cheers,
Torsten