I'm thinking along those line too. To sum up what I've experienced: the EATC issue started with intermittant fan operation. I replaced the fan controller, to no avail. So I swapped head units, and in so doing, no head unit since plugged in has operated correctly. However, it is powered, at least in part. The lights come on, and after about 10 minutes of operation, random bits of the LCD light up. This is true for when I replaced the head unit, and for when I put the original back in again. The random lighting is the extent of what it does; at this point it will not enter diagnostic mode either, nor will the rear fan operate anymore.
To be clear, the original at least outwardly appeared to function correctly before pulling it out, even though I didn't have complete system operation. Also of note, prior to swapping the EATC, the message center worked fine. After, not at all. I know they're tied together, so that is suggestive as well.
So, I agree, that does seem to suggest that there's a issue in how the EATC head unit was connected. Or, at least, with the wiring that it plugs into and it was disturbed when I messed with it. Maybe the best fix is to find a replacement for the dash harness, or the EATC portion. The trouble is that Explorers with EATC don't commonly appear in the junkyards. There are too few of them with the option, it would seem. I don't particularlly want to give up on the system, but I'm not sure how many choices I have.