yeah getting something sturdy enough to leave out all winter through the storms and everything would be a challenge. The good thing here is that it doesn't have to be quick or easy...even if it took all day to set up you could put it out after thanksgiving and fish till april so it would be worth it!
Drafty is very bad (lots of 20 to 40 below and colder times here). It would have to have serious seals between each wall, roof, floor piece and especially between the two halves. Maybe some sort of camlock or other serious tension device binding the two halves together on a thick seal.
Really I think the roof would be the toughest part - it would have to either have some columns inside to support or just clear span the width (not that big of a deal over 8 or 10 feet), but worse than that it would have to have a clever seal where the two roof halves met to make sure it didn't leak...
I think a smart enough guy could engineer something that could be sturdy enough (I'm not that guy...but I'm thinking maybe bolts embedded in the floor that stick up like studs - put the wall over then tighten the nuts down - then more bolts from wall to wall to connect each corner. Same for the roof. Connecting the two halves may be tougher than the walls.