I'm all for adding Griezmann, but how/where would he play in our squad under Mourinho? I don't see him as a traditional right winger as far as providing width and speed for crosses. He'd prefer to play centrally behind the main striker - a spot currently occupied by Rooney, so either Wayne would have to be moved further back (doubtful due to his age and skill) or they'd both play in lieu of each other.
You'd hope Jose would be good enough to not go into the season thinking Rooney is good enough to be the star player, LVG took the same risk and it cost him his job.