I would book it as a face VS tweener match. Punk would not have to turn heel again if his momentum continues, but at the same time there is no way he would get a more positive fan reaction than Stone Cold. Both guys should just be themselves in this feud and that would result in a face Austin and a tweener Punk. Punk could give Austin a hard time about his drinking, and many other things the two characters would potentially disagree on. As for the match itself, Punk must win because Stone Cold has nothing left to prove. It would make for a decent Wrestlemania moment.