Very interesting, and probably doesn't help your ceiling fan situation, but on my 2015 27K I did the same modification. That is, removed the living/kitchen area vent and replaced it with a fan.
As you can see in the attached picture, when I removed the old vent I was relieved to find that the opening was already wired for the fan. The power leads shown are now used for the new fan, and is not controlled by the overhead lighting switch.
I guess there must be a lot of variation in models and years as far as wiring goes.
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