Outdoor rabbit indoor to back out?

Hi, I need advice. 1 week ago one of our rabbits who have always been kept outdoors and nearly 9yrs old got attacked by a stoat. Unfortunately we had to put him to sleep.
However when we got back from vets the stoat was trying to get to our other rabbit. (They had separate hutches) so in a panic we brought him inside brought an indoor cage and put him in our sons room.
The rabbit is not happy and spends most of time just laying in the litter box.
We were wondering if we got a shed insulated it somehow, whether he could go back outside.
I know usually the advice is not during winter time but was wondering as he has only been in a week whether we could do it or not.

Thank you for any help/advice

Hello there. I am really sorry to hear about your rabbit. It is possible your other rabbit would settle indoors but he probably finds it a bit scary. If you were to get a shed then your rabbit will still have his winter coat and won't lose it after 1 or 2 weeks of being indoors. (I shouldn't think!) Good luck with whatever you decide.