Why couldn’t the Micro Controller be placed on a separate daughter card e.g. “Stamp” or “Arduino”. Then it could be upgraded as needed?
A standard interface PCB would be used with the different Micro Controller daughter cards to makup the complete controller.
That concept would also allow different Microcontrollers to be used, e.g. dsPIC, STM32, ARM, etc…..
Just a thought that I have been kicking around for awhile ???
-Mark