What do people think about the protagonist and antagonist switching places halfway through a story, before coming together at the end to defeat a greater foe? Say, perhaps, there are two people (A & B), both after the same prize, and A spends the first act trying to steal it from B. The sympathy then switches to B, who has to get it back. Finally, A & B have to unite to defeat a larger foe (C) in the end. The immediate problem I can see is, in building up the sympathy for whoever is in the inferior position, the other will come out looking like a jerk, and that will ultimately undermine the sympathy for both characters in their final challenge. Any thoughts?