If John Carmack is a 10x programmer, then trying to find 10x people for your organization is an absolute lost cause unless you're willing to shift your entire organization to be what he wants to do. Because there's only one Carmack and he does whatever the fuck he feels like.
I wouldn't go that far. Yea he made Wolfenstein 3d, but he started his work only after seeing a demo of Ultima Underworld (which was a much better 3d engine and complete game).
He is good at optimizing and using algorithms, but I don't think anyone says he is that good at writing programs. He popularized and sped up a lot of the techniques already in use. Raycasting wasn't anything new when John Carmack used it to build Wolf 3d (it was described as far back as 1982, 9 years before Wolf3d). It was also used in other games by other developers around nearly the same time, with games that were in development a lot longer.
He would probably figure out common patterns/requirements between them and build the best CRUD framework ever (possibly in Haskell), the only problem is that he would be the only person smart enough to use it.
Being 10X for a short duration is much easier than maintaining 10X over years. And also, are these people successful in terms of personal fitness and health? Is their home clean? Do they have good relationships with their family and friends? Do they spend time socializing, or do they spend all their time working? If being 10X is true, why haven't they figured out how to get rich yet?