Why is Hummels is being touted as an alternative ?
He is just 25 yrs old which means he has at least 7-8 good years unless he has a major injury. The only reason could be that the board knows he is unavailable and just throwing his name so that they can say they tried other options when Marcos was not available and couldn't get him at the end.
I think the reason Lucho wants (if he indeed does) Matheiu is that he is a CB/LB combo ala Abidal and so we can move to 3-4-1-2 as we used in pep's era. Only this time, we will have a proper CB instead of Bussquet covering. Maybe Something like this :
------Neymer/Pedro--------Suarez---------
---------------------Messi-----------------
---------Iniesta------------Rakitic----------
-----------------Bussquets----------------
---------------Mascherano----------------
-----Mathieu-----Pique/CB-------Bartra/CB--
Alba instead of mascherano when we need more width/attack. Against avg/lower team, the back line would be Alba - two of Pique/Mathieu/Bartra/CB - Montoya/Alves with Bossquets/Mascherano rotating at DM.
This actually looks rather good. With a solid 3 line defense and Mascherano as defensive screen, Bossquets at his typical creative DM role, opponents gonna have tough time penetrating our box. Meanwhile with the Ney/Messi/Suarez/Iniesta/Rakitic will keep their defenders/wingback/midfielders very very busy wrecking havoc.
The only scenario where this needs to change is against Real who had the best attack after Barca. Then Montoya/Alves instead of Rakitic for more depth in defense and to contain Ronaldo/Bale.