Well, such an 'experience' is possible with their Edgewalk attraction, where they hook you up to a safety harness and then you practically dangle off of the top of the tower.
Many people are quite frightened when they go up there, but most of them manage to overcome it and hang off the edge of the building. I'm not going to lie though; I would not be one of those people. Not even to 'save face' would I be that high up, let alone outside at that height, not even thinking of hanging off of the building! That's just how strong my fear of heights is.