Since the micro listens on the TX line, I could have it just check in for traffic and if it detects there's no hashing going on (so, cgminer was killed) it resets back to hot setpoint to be ready to restart mining. I'll have to look into exactly what traffic gets sent when cgminer is still operating even though the board is down to know how to detect that condition, and I don't really have time for a while.
Possibly the code could increment the cold setpoint every time mining fails and is restarted. One problem with that is you couldn't optimize per-board since both boards would detect cgminer restarting and both increment even if only one needed it. Also, unless it was saved to EEPROM, the new setpoint would be lost every power-cycle. If it was kept, without a means of resetting back to defaults, over time the setpoint will drift higher and higher due to internet downtime, manual reboots from software and other issues.
I would say once you have some time the traffic might be a good place to get some more reference from. I really like the idea of hot/cold script If only there was relm for small flash memory instead of EEPROM.