It's a very interesting analysis, I really enjoyed reading it. The thing is that when you ask a central midfielder to cover the side everytime the fullbacks go forward not only the CM will get burned after some of those runs.
You think Vidal would be exhausted by half time if Juve asked him to cover an opposition fullback?
Plus the AM oftenly play a free role without any defensive responsabilities so asking him to drop back everytime the CM covers the SB will get you with 2 players (CM and AM) burned out after just the first half of the game. Imagine recovering the ball and having Mata next to Pirlo, Vidal and Asamoah on the sides and 20 meters away from the strikers without any player to link them.
The days of the trequartista being allowed to be a pure luxury player are long gone. They are all expected now to make a defensive contribution.
And why do you think dropping a bit deeper into midfield to fill a a space would be particularly tiring? I'm not suggesting you are going to ask a trequartista to go into midfield and play like Gattuso.
And when the trequartista drops deep, one of the strikers drops a little deeper to avoid the team getting stretched and and to avoid the gap between midfield and attack becoming too big.
Your attacking shape and your defending shape don't need to be the same. You could easily be a 4-3-1-2 team when attacking and then drop back into something that looks much more like 4-4-1-1 when defending.
Are you against 4-3-1-2 because you believe it involves having three players in the team who should do no defensive work? Because I believe that is a flawed viewpoint for a number of reasons.
Go and watch all the long passes Iniesta sends to Alves where appears free as a winger cuz all the team is marking the other side.
But it doesn't matter because Alves doesn't then cross it because Barca have no-one to score from a cross.
All they are trying to do is stretch the game out enough to try and penetrate the middle, so the teams who have done well against Barca are the ones who refuse to give up the middle of the pitch.