It's too late. All these ideas are centered around the manager. If he's not good, nothing will work. The good part is that many of our new players are young and will get a sold chance with hopefully a competent manager in terms of possession attacking football. Whatever Valverde is, he has no clue how to build attacks in possession. Anyone who watches our games with a bit of a critical eye has seen this by now.
Also, you can drop Messi deep and play him at times as a deep lying playmaker, but for this to work well, two things need to happen. Messi needs to have defensive roles if the ball is lost, because the play will catch him in a sensible position for us, one that if it is not blocked, it can hurt us. Which means he has to run, track opponents, cover ground, intercept and do a bunch of defensive things he can't do and is not even willing to try to do.
Because of this, we cannot allow our other midfielders to go up, leaving Messi alone and providing him pass option up front. Because of this, when Messi drops, you can see that nobody takes his place. This happens because if the ball is lost, Messi will be a non-factor as the temporary DM. Which means Busi and Rakitic need to stay back.
The basics of fluid football say that a player can momentarily take up the position of a teammate, but when you take the position of Rakitic for example, and allow Rakitic to move up, you also need to take the initial role of Rakitic, not only on the ball, but also off it. Roles are tied to positions, not to players. Messi being in a DM position means he has to do the DM work in that specific play.
To put it simple, Messi cannot effectively appear as a deep lying playmaker, because he can't do the required things if the ball is lost. Which means the player who was initially there has to stay there. This basically means we lose 1 player from the attack, because the position Messi vacates is not occupied by another player from Barcelona. Hence the big holes in the images. Positions Messi vacated that weren't occupied by somebody else.