Serious gamers, especially folks who've been serving as game masters for some time, would also be good to put in this role. We're used to thinking on the fly, bringing in different things to hinder, confuse, or kill off (depending on our moods, of course... ) our players.

Seriously, a good GM has to be able to immerse himself at least partway into any role that's thrown at him. Gamers from the early to mid 1980s are especially good at this, IMO, since the computer crutch wasn't developed yet. Even a computer gamer isn't going to be as good at the sort of non-linear thinking that we're talking about here. Computer games tend to act (and react) in certain patterns, while a good RPG never really did.

To properly game or test a situation, you need someone who's actively trying to break it, someone wandering around throwing spanners in the works, and a group that's actually trying to follow the plan. In a decent RPG, the GM takes on the role of both the random chance and the person actively trying to break the plans of his players (within the framework of the game and certain conventions, of course). You would certainly get a lot of "non-school" solutions from such people.