Ford territory transmission limp

I notice these days that dealers do not add a separate transmission cooler when people option a tow pack. They seem to think that having an integrated transmission cooler in the radiator is sufficient for towing, but I know for a fact that this is not good enough. I have a RWD Ford Territory that has a four-speed auto and a dealer fitted genuine tow bar, and I had the same issue with transmission light coming on while towing that Toyota HiLux owners are complaining about. In my case the transmission go into limp home mode - stuck in 3rd gear. The camping trailer that I was towing was nowhere near the maximum limit; it was about half the weight. The dealer didn't want to fit the cooler as they said it wasn't needed, but I managed to buy one through Ford parts and fit it myself and got them to flush the transmission fluid as it was already burnt. When the transmission fluid heats up it burns and loses its efficiency to cool the transmission, that's why a good-sized cooler needs to be added for towing. High automatic transmission temps are the number one cause of transmission failures, talk to any auto mechanic. So if anyone has had that light come up, fit a transmission cooler and get your auto flushed/serviced.