Arteta's job is to be able to maximize the left winger because Arsenal's left winger's game is often inconsistent.
You're right and it appears that they're trying to bring Eberechi Eze back to where he started his football career
[source]... He's definitely an upgrade to our current attacking players on the left wing and in addition to that, he can play in multiple positions
[something that Arteta loves].
Besides Manchester United showing interest in him, Arsenal are also preparing to make an offer, so this does not guarantee that he will move to Manchester United.
Arsenal likes Watkins and they've been linked to him in the previous transfer windows as well, but I haven't heard from a solid source that they're preparing to make an offer for him... Would you mind sharing the source?