Bill,

So you don't want to send any other message type other than Patch Numbers. This means all Patch Programming occurs on the individual midi devices and is saved on each.

Also from your explaination you separate each midi device by channel (device1=Channel1) (device2=channel2) etc...

I think i would be tempted to just modify the PAIA Fader to also issue the Patch Change connecting the LCD (and perhaps key switches) to the J1 expansion port.

Otherwise, scanning a keyboard is covered generously on this site. LCD display is an ever present topic also available on this site. I would suggest a '51 variant with internal Flash instead of external 'PROMs but there is good logic to using what you have.

regards,
p