First, I don't see Audi coming in over Porsche. Lamborghini or Bugatti, sure, but not Audi.If Volkswagen Group would enter F1, they would probably do it under Porsche or Audi name, but I can't imagine them being only a engine supplier when Mercedes is there with their own team
Second I'm thinking baby steps. Engine, then buying a team. Starting from absolute scratch is HARD and since they are a manufacturer, they can't really do it Haas style can they?
Apparently the Alfa Romeo thing at Sauber is being de-emphasised so maybe that team is suitable for Porsche. Or they could take over Toro Rosso, but then maybe Lamborghini would make more sense than Porsche.