He would SOLVE ALOT, the main issue in this team is midfield.
A big upgrade in midfield, and everything is smoother, defence improves because we keep possession easier in mid so they the defenders dont get exposed on counters due to inept mid being allergic to the ball, ordefenders not having too much of the ball anymore (as they do constantly now), which constantly leads to fatal giveaways in the press. Plus attack improves because we would create way more for them.
I dont think it is anymore, I think the flanks are a much bigger issue. Just this preseason I saw multiple instances where one of our midfielders made a progressive pass out wide only for Sandro, Danilo, etc not advance the ball or just straight up pass it back. Kostic and Cuadrado should help when they're playing, but they cant play every single game so they will be exposed when only one of them is out.
SMS seems like a luxury signing at this point. Obviously it would be great, but the focus should be on those other positions imo