It's one thing to have work rate and be effective going forward, quite another actually being able to time a tackle and, far more importantly, have the positional intelligence. Those aren't things you just pick up. Whatever people say about Alves, when he actually tries, he can defend, as he's played that position all of his career. I think it would be naive of any of us to think that the ideas we come up with haven't been considered by a professional football manager, who sees the players day in, day out in training, thus I am inclined to go with their take on tactics.
Well, then we must try 3-5-2.
----------------------------GK------------------------------------
----------Bartra--------Pique---------Mathieu---------------
---------------------Busq/Masch------------------------------
-Alves/Doug/Pedro-----------------------------------Alba--
-----------------Messi--------------Iniesta/Rak-------------
----------------Suarez--------------Neymar-----------------
This formation would play into team's strenghts IMO. Alba and RB can concentrate on attacking duties and Messi and Iniesta/Rak can play more centrally without the need to cover for fullbacks. And Suarez and Neymar can play as inside forwards, instead of wingers which suits them best too.