I don't buy the "out of position" argument anymore at this point. That doesn't explain everything about his awful form. He mostly plays in the same are no matter if it's 4-4-2 or 4-3-3 on paper anyway and the mistakes he makes don't just come from playing 10m higher or deeper.
It's not like we use him as a CB or something, the difference isn't that big. He just plays worse in pretty much every aspect of his game no matter where he plays at the moment.
Why that is? Who knows. Maybe last season he didn't feel as much pressure seeing as he was still a new signing, everyone knew he needs time. He couldn't play in CL anyway and we still got Iniesta etc but after the summer the pressure was really on. He knew he had to deliver now, he had his time, Iniesta is gone, now it's on. Dembele had his problems outside the pitch but even at his young age had the confidence to come back even after media fired at him nonstop where Cou seems like it's really getting to his head. I don't think a simple change up in formation would fix that.
Maybe another manager yes, but not because that one would call his position LM or put him in midfield, more because Cou may need some other type of manager than Ernie just from a personal relationship point of view. But in the end the enormous fee will always be there, the high expectations will always be there. Either he can deal with it and this was just some long ass streak of weak form or he's not gonna make it.