He's got more job security than any GM in the league. The only way he can lose his job is if he commits a crime or dies. Or maybe if he got drunk and started teeing off on Gayle on his radio show. Short of that, he's not going anywhere, no matter how bad the team performs. That is unique among the 32 teams (well, 31 when you factor in Dallas). He's more like an owner than a GM in that way.
So, for a prospective coach, it's not much different than going to work for Jerry Jones. In either case, you know the GM isn't going to take the hit if the team sucks.