Does my plan make sense?
Yes. Perfect sense. That is the advantage of having an indoor and and outdoor enclosure. I am doing this exact same thing with my twenty 1-2 year old russians. I brought them back indoors a little over a week ago and I am feeding the bejesus out of them and soaking daily. They had slowed wayyyy down on the eating outside due to the colder night temps and shorter days, but since being brought back in, they are cleaning their plates daily again. I intend to fatten them up for another two weeks, then clean them out, cool them and get them sleeping in their fridge by early to mid December. Then using the same indoor enclosures, I will wake them late Feb. and gradually get them back up to speed and eating. Once the warm temps return they will get longer and longer periods outside until I can start leaving them out 24/7 again like I did all summer this past year.
Our day time temps are fine for them most of the year here. Its the night temps that prevent me from letting them live outside longer. We were 80 degrees today, but night temps tonight will be low 40s to high 30s. I'm considering adding some heat to their night boxes, so I can leave them outside more. I would only need to heat it to 60ish to accomplish what I need. I think a RHP on the box top coupled with a thermostat would do the job nicely.