I rate him quite highly as well, provided some great service in the WC final before his substitution (and looked much better than Aguero). This signing would show immediate intent, as we have young wingers already (Coman+Berardi). I'm more interested in someone who is a known commodity and can perform now for us. Still has a good 2-3 years left and by then Coman/Berardi should be ready for regular first team football.
Edit: Also, what more appealing younger options are still available? Shaqiri doesn't appear to be moving, or would cost a good 10m more, though he does fit the bill of young and quality.