Coquelin might very well be a flash in the pan but what if he isn't? Can we justify spending £25m on a position where the player in question is not a significant improvement on him? I've never said Schneiderlin isn't better but is he that much better we should spend big on him? We don't have £150m to spend this summer so we need to spend on what we need rather than shore up one position. Schneiderlin is a fine player but this isn't Busquets we are talking about here. We could play both in certain games but we play more games against weaker opposition than better so what happens then? The area where Schneiderlin is clearly better is his passing, ideally I'd rather have him for that but he won't come cheap. If we could get him for around £15m then yeah I'd take him but Southampton will want a lot more.
And the type of player I mentioned doesn't fit the description of him at all. I'm talking more of a player in the Gundogan/Veratti mould, guys who can dictate and run a game. Players who can put in a defensive shift when required but also compliment the attack. We don't have a single player like that in the squad, Jack is unproven + injury prone and closest thing we have is Arteta but he is past his best. I'd rather spend the money there, Arteta will do as backup for another season. He'll hardly play so should be able to keep himself fit for a longer period in the season.
Like I said I'm not completely ruling it out but if Coquelin maintains this form I can't see Wenger spending big on him. The biggest concern with Coquelin for me is his passing needs to be better.