I've watched the video. Interesting. Some problems though.
First, I don't think we need to have Busquets dropping deep and form a 3 line when we attack. Most opponents against Barca go with a 4-5-1 in defense, almost all of them do that, including the top teams. At most, they will make a 4-4-2 defensive setup. But the 4-5-1 is by far the most used defensive arrangement when up against Barca. Because it allows a close 3 in midfield, while also having two wide midfielders who can make pairs with the fullbacks and block the wide areas.
We don't need to be keeping 3 at the back to guard only one attacker from the other team. Way too cautious imo. Busquets can very well go up in front of the two defenders and play as a DLP. Valverde will find out that he will have more control than at Bilbao due to the increased quality of the ball and our philosophy. Teams will create fewer chances against Barca, and he will have to find a way to create superiority in attack against an opponent who simply defends with more players than what we can attack with. Under these conditions, you can't sacrifice a player with Busi's passing range for more defensive security. Wouldn't be the right thing I think.
Second, I'd like us to be less focused on the actual opponents as it's the case with old school defending tactics, and more focused on the ball. An opponent can only hurt you if he is passed to. We don't have to stay extremely close to the opponent to mark him, we just have to make passing to him very hard to pull off in one move. In modern tactics, there is a concept called cover shadow, which says that you can also block a player by placing yourself on his pass trajectory. if I stand in front of a player I actually block him, by making him inaccessible to his teammate. I block the pass to that player and I also obstruct the vision of the ball carrier. And also, by not standing right next to him (as in marking him), I gain access to other players and I can also move towards the ball putting pressure on the player who has it. This is illustrated bellow.
So, in this example, if my LCM is staying very close to the 'option 2' player, some other players need to stop the player with the ball (meaning an opponent somewhere gets more space because every extra player I bring in an area means more space somewhere else on the pitch). So, basically, if I stay here way too close to option 2 player, and if some other player can't pressure the guy with the ball (Neymar is too far), he can advance with the ball until he is approached by one of my players. And if he is not approached by anyone (because it's not their man to handle) he can very much go all the way to my 16m. box. PSG did this a lot in the 4-0 loss (see Meunier and Kurzawa's runs).
But if I don't block the receiver of the pass, and, instead, I only obstruct the trajectory of the pass, it makes that pass inaccessible. I do not longer react to the player itself, but to the situation and the position. In fact, am I the one who makes the opponent adapt even if the opponent has the initiative. This is the sort of aggressive defense we need to impose again. Not to mark the players out, because in this case, every marking mistake can lead to a conceded goal. But to control which passing options I allow the opponent to make (some passes are more dangerous than others), and which passing options I close down and control. In this way, I can very much predict where the other team is going to play, and I can then take measures to fortify those areas. This is very much based on the belief that the other team will pass in the areas that are more free. So if I decide on purpose which are the areas that I leave more open depending on where the ball is, I basically know how the opponent will play (to some degree). This is so much better than trying to pull off a traditional type of defending. Which is not feasible with the players we have.