I've updated github for new Gerbers, parts list and 3D renders.
Now takes into account changes for Avalon protocol docs.
Need to stew on this a few days to find errors and then can order first boards.
Going back to the unique ID per board, I think there's an easier solution instead of using a serial number, why not have a set of say 8 jumpers or dip switches on the boards, so we can configure our own unique IDs with those, that'll give you 256 different board ids, assuming the PIC can read the jumpers.
No free pins for that on the PIC, and that method costs money and requires user intervention. Putting a serial# in the firmware is transparent to the user and doesn't cost anything.