Transfers:
For this to work, we would need a left sided, left footed defender, who can go forward (which we were already looking for last summer – Van de Wen)
To this position it would be natural to get Hincapie to follow Alonso (if not, then Schlotterbeck, Bastoni or Inacio). We would also need a backup since we currently have no payers for this position.

Other than this we could recreate his formation with the current players just with the left side (Robertson/Tsimikas) doing Leverkusen's right side's job (Frimpong) which is going forward while staying wide.
Our right side (Trent/Bradley) would then be able to do their left side's job (Grimaldo) coming inside, joining the midfield in possession.
Maybe this could be opposite with Tsimikas and Bradley.

In midfield, he plays with a box (ish) with wide attacking midfielders rather than wings. This would support Salah in his new more creative and assisting role from a more central possition. And Szoboszlai could be deployed in his old Leipzig role as a leftsided CAM cutting inside and creating rather than box-to-box as he is now.

Lastly, for this box to work, we'll need a double pivot and substitutes for both. Macca and Endo are the natural choices. Beyond them, it would be Trent and Gomez for rotation why we could use another body there. For this Alan Varela or Joao Gomes would be perfect.

Here's how I think the players will/won't benefit from Alonsos potential arrival:

*Szoboszlai/Gakpo/Elliott – benefit: Left and right sided CAM would be perfect positions for them respectively
*Trent – benefit: Less defensive responsibility
*Nunez – benefit: more of a lone 9 feaded by midfielders

*Diaz – disadvantage: lack of winger role for a full blooded winger (would be open to sell for the right price as he might be abundant)
*Curtis/Mac Allister/Gravenberch – disadvantage: fewer box-to-box roles (they'l have to play double pivot or fight for wide CAM roles)