If im right each temp sensor has a unique address that you could use to determine the ID of the overheating dream chip. How to deal with it is the problem. -- my suggestion, and others jump in if I'm not thinking logically ....
Well there is an on/off switch for the fans. If your fans derive power from the led driver dc power source with a
dcdc buck regulator then coopting the fan on-off relay to turning on-off the Power to the LEDs would turn on-off fans in unison too. I cant imagine you would want high power leds on and fans off. This is why you might want to have a fan control function and ss-relay on your "Esben card" 5 channel stackable driver card. If you wanted to address many different fans/dream chip pendants then there is the problem of not enough arduino mega pins spare to do it. In that case there might just be enough pins left on the Arduino mega for a shift register
mux to expand the fan on-off pin to multiple instances of on-off control for as many dream chimps as you have a need for. Of course this would need some programming (and a nice donation maybe).
That is, what I'm suggesting is have a on/off relay on the driver board at the dreamchip, drive the fans from their local led DC power source and when the arduino can identify an overheating dreamchip with its addressable temp chips, it could shut down only that dreamchip and it's fans together by using the mux addressable relay. Maybe you might want it to also sound an alarm and leave a flaming lightbulb icon on the default screen to warn you the fans or the heatsink of a pendant might need maintenance.