If left outdoors, they will need to be able to access mud for hibernation which is below the frostline. I kept them in such a "semi-wild" state when I was a youngster, and the stress of wondering if/when they would appear in the spring was almost overwhelming.
Snappers...for the person who can provide the space and conditions they need...are an absolutely fascinating species; one of those animals that are frequently overlooked because, although impressive, they are common rather than ultra-rare. If Snappers lived in a remote swamp in Siberia and were rarely collected or seen in the hobby, everybody would be clamouring for them. It seems that many people in our hobby only want what they can't easily obtain, and/or what others don't have.