> every minute, ask every server in each location directly for the temperature from its onboard sensors, take the average, and if it’s elevated, blast an alert out to everyone on the systems team to check for datacenter overheat.

I've once done the opposite: the office "server room" (a small room with three racks, two of them for the patch panels, one for the servers and switches) was cooled by a mini-split which was prone to locking up with the compressor enabled (the relay which controls the compressor got stuck) and freezing, which then stopped the air from circulating due to all the ice. I wrote a script which ran on one of the servers which read the ambient temperature through IPMI to detect when the room was too cold, email a warning, and power off (using ssh) the neighboring servers and then itself.