I can only imagine we're going for him if Aaron leaves but, if we plan to play 3 in midfield then numbers wise we could technically sign him even if Aaron stays.
Ramsey - Xhaka - Torreira
Benega - Elneny - AMN
It's not actually too much and is arguably necessary to cover for injuries or cover us if Xhaka and Elneny end up being shit again. We'd then have Ozil, Mkhi, Laca, Auba, Iwobi and Nelson for the 3 forward positions presuming Welbeck and Perez leave. Lots of depth and plenty of quality too.