Sounds like you should try it and see how you like it.
We turn the fridge off when we leave the boat, but that is for months. I built some nice vents to go over the open hatches and they worked well this past year with no mold
but I'd like to leave some fans on in the boat and bought some....
... low voltage switches to do what you are talking about ...
Sure Power Low Voltage Switch 130512 | eBay
...here is the tech sheet....
Hopefully I can wire them in before we leave and give them a test run.
Our two controllers (Blue Sky 2512iX and 3024iL) have a load feature and can do what your are saying, but only if you also have the IPN remote
and we don't have that on either boat.
Let us know how it worked and which controller you are using,