IMO Aouar was going to be the Xhaka replacement but we were given an either/or scenario and went for Partey instead.
That said with his current contract status we could still well sign him in the summer and have our twin playmakers ahead of Partey as #6. Aouar would also improve our goal capability from midfield.
As for the defensive cover = IMO if Partey can be as effective as he has of late with Xhaka not likely to be of any assistance, then he can do so with Aouar who is more dynamic and press resistant.
I'd take Aouar ahead of the likes of Coutinho or Hazard because IIRC he will be a free agent or close enough to it that he will not cost a bomb. I think we will try to look for cost effective options re CM because there are options out there that we can get, and then we can load up on our ST/CF options, as genuine goal scoring forwards are at a premium and clubs will want big numbers for them in order to sell.
And just because I really, really, really strongly dislike Xhaka and any move to retain him beyond the end of the season is an automatic fail for mind, as I will never forgive him for his strop when subbed off v Palace.