I would find the best trailer to use in cold weather areas and high quality etc first. You can always add a wall to separate the toy garage area to suit your needs.
I suspect the whole toy hauler area can all be changed around to suit your needs. The fold down beds from the wall or ceiling makes it great to use when you are not hauling the toys...
A local friend of mine got one of those Keystone OUTBACK Loft trailers which had the side ramp for loading. He tricked the whole thing out for his liking... Loved the LOFT area for sleeping up above everything in the woods haha... Have no idea about running in the cold country however...
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Roy Ken