Khedira will 100% start the final if he makes it, no need to pretend otherwise. And I sincerely hope he makes it. For this formation, especially in tougher games, Khedira is a must. The unpredictable box to box element he provides is necessary (even if he is a fucking awful finisher), as is the clever tactical physical shape he provides. It matters less, for now, atleast in this formation, that Marchisio is technically the better player, passer and all around midfielder. For this set up, Khedira is a must if he is healthy. It will be another matter to adress if or when Marchisio gets back to his physical strong self next season, then we can truly talk of him benching Khedira.