Do you already have the fan in place? Or are you thinking of adding a fan that doesn't exist yet?
When we first purchased our Outback we wanted to put in a ceiling fan. We found 12 volt DC fans just fine, no problem. I had a spot where it could easily be installed without any extra wiring or anything. Seemed like a perfect idea. .... until....
I realized that if the opposing slides were both retraced (in), they would both hit the fan. The ceiling wasn't tall enough for the fan to clear the top of the slides, and if I lowered the fan, it would have to hang so low it would clobber us in the head every time we walked under it.
We just oped then for some nicer tower fans that can be moved around. Been using them ever since. That's not the "ideal" we wanted, but sometimes, things just don't work like you really want, and you've got to go to Plan B.
So, if you don't have the fan already in place, make sure you have the head-room and the clearance away from slides when retracted.
To answer your question, yes you can run a wire anywhere and put a switch on it. The question you need to ask yourself is, how much work do you want to put into the project to conceal the wires? Nothing says you have to conceal them either. It's all up to you.
Personally, I'd go with the remote and then use double sided tape sticky stuff and mount the remote to the wall so it's always at the same place and no chance of getting lost. Change your batteries on a schedule and they will never have problems with dead batteries that way.