#3 Unleash Neymar's true potential
You don't need stats realize that the Neymar who turns out for Brazil is vastly different to the one that takes to the pitch in the Blaugrana shirt. With Barcelona, Neymar's focus is mostly on assisting from the wings - very rarely does he cut inside for Barcelona and carry the ball.
To be fair, when you have the likes of Suarez and Messi making brilliant runs into the box, you could forgive Neymar's proclivity for choosing the assist. Witness the Brazilian's performances for the Selecao though, and you'd be crying out for the player who grabs the game by the scruff of the neck for Barcelona.
Messi's presence in midfield would allow Neymar a greater responsibility going forward, and I'd bet he would thrive in such a situation. We might see him be more willing to dribble his way into the box and score some of his trademark wonder-goals. Barcelona need to make Neymar their #1 asset going forward to ensure he stays, or the Brazilian might take his talents elsewhere. Messi dropping into midfield would allow Neymar to not play second fiddle to the Argentine anymore while keeping both egos satisfied.