An excellent solution. You might find that you get tired of moving the tractor in the good weather months anyway. I did after a month. Plus when I went to visit my grandkids it was a lot easier to find a chicken sitter that did not have to move a tractor.
I find having an extra place I can...
I'm not sure if you are in Sudbury England or Sudbury Massachusetts. Two different climates. Or maybe somewhere else.
You can read a lot on the internet. Some internet information is accurate but that is not correct. Their down keeps individual birds warm once they are fully feathered out...