I've always thought Griezmann was a replacement for what Rooney was? I assumed he would eventually be the main striker with Rashford backing him up. If Zlatan doesn't decline next year then he would play off the left with Mkhi on the right and Pogba in front of the midfield with that Bakayoko guy coming in to rotate with Herrera and Carrick (based off the recent rumors).
Perhaps it could be seen that way, with them nominally being positioned in the same area of the pitch just off a striker. Equally so, Rooney has made a lot of sacrifices and has been marginialised to get in the team.
The problem with Griezmann is that if you want to get the very best out of him, he has to be allowed to roam and do what he wants when he wants with nobody else getting in his way or taking up the pseudo position he has drifted into. It doesn't really matter what it looks like on paper - Griezmann, at his optimal best, is going to break rank from it and do his own thing. Furthermore, if he is being told to stay within a set of positional boundaries, it defeats the point of bringing him in for a fee north of £80m as you may as well get a specialist in who is not having to compromise and is perfectly happy to stick to the remit of a set position.
I'm sure if Griezmann came, he would try his best to stick to any job he was given and it wouldn't be an issue of him complaining etc., but at the same time, he'd be sacrificing a large part of the very same game that has elevated his status to what it currently is if he did that. Perhaps he could reinvent himself, again, and become a 'boxed in' player, but that's one hell of a high stakes poker game... or a colossal waste of money and time should he not manage to do it.
I'm sure I'm not the only one that thinks when you buy a ready-made star who has shown the world what he can do via his body of work up to that point in time, you leave him to do exactly that for you and try to do everything in your power to facillitate it, even, by building the team around him.
It's the exact reason why anyone who watched Pogba knew that he needed that left-sided position in a three to come alive and that stuffing him into a two or whatever and asking him to be something he never really was would garner less than optimal results. The player will gladly try, but it's abundantly clear he has a niche and is being wasted if it isn't being catered to.
For me, if you put Griezmann back onto the left, you've already taken away half of his options and game. He isn't Neymar or the like who organically drifts over to that side of the pitch and even though he thrived in that position for Sociedad, he has come a long way since then and flourished with the vaster field of vision and opportunities he gets when played through the middle.