Fridge DC switch question

[ThePair]

I'm putting this out to all the experts on this board:

As many others have done, I installed a switch on the outside of the TM to allow me to turn off the power to the fridge when it's on battery, so that while towing, if we stop, I don't have to worry about the fridge draining the battery. One of these days I'll post a pic to show it, but it's not much different than what others have done--I cut the black 12V wire going to the fridge, attached some left over 10G wire and routed it out to a waterproof switch that I mounted on the underside. Works like a charm, tested with a voltmeter.

Here's my question. I once forgot to turn on the fan, and needed to pop the shell back open just to turn the fan on. This got me to thinking: If I splice in a little wire from the "downstream" part of my switch, and connect it to the hot lead of the fan, this would mean that any time my switch is on, the fan will be on, regardless of the interior setting (power tapped off the fridge 12V line). However, if I have the interior switch "on", then the fan will remain on regardless of the exterior switch (power from the normal line). This, I'd think, would be beneficial for a few reasons--still have interior control, if, say, I wanted to try to help the fridge on a hot day, but could still activate the fan from outside if I forgot to turn it on again. Or, if I store the TM in the garage with the fridge set to DC and fan off, I can turn both on 24-48 hours before a trip, to allow the fridge time to cool off without needing to pull the TM out. Or, leave the fridge on AC but unplugged, and then plug in, flip switch so that the fan is on, but with AC power for a faster cool-off.

Anyway, my question is (1) is this feasible, and (2) are there any unforeseen issues? Would tapping the fan's power off the same lead as the 12V to the fridge cause an issue with either? Would having both switches on (power coming from two sources) be an issue?

I'm no electrical engineer, so I put out a plea to those with far more experience than I.

Thanks!

Marc