The idea is good when the whole team is fluid. It similar to Koemans 343 on that mini run where you have a bank of 5 in offence and a bank of 5 in defence. Just this time you have both fullbacks become left and right defensive midfielders.
Long term you would need prime Alves or Kimmich (or Sergi Roberto at his peak for that matter, a fullback in their prime who thinks and plays like a midfielder basically, rather than a lateral running machine) on both sides- and that isn't easy.
The offensive widemen need to both be excellent individual creates as their will be moments (periods) of the game where they won't be supported by overlacks.
Basically it is a high level system which needs excellent lateral players at their peak, which we absolutely lack. Maybe it worked in Qatar where the technical, phsyical and financial level of Al-Sadd was above anything in Qatar (yet below most of the opposition in ACL where Xavi consistently failed), but it won't work here without 200/250 million which we don't have to sign the best DL,DR,AML,AMR around.
So basically we are seeing a limitation of Xavi in the disconnect between the way he wants to play and the players he has at his disposal. So much so that he wants to bring in a 39 year old Alves and renew a injury prone Roberto to try and reenact it.
God gawd, and with that I just gave an indirect ringing endorsement of the Crouching Basque Tiger Ernesto Valverde
, who worked without the contraints of what he had. The guy didn't even need the team to run. They worked around running