I don't know whether he'll be any improvement.
But it seems that our only way of playing will be: Messi as a false CM-CAM in the middle, trying to dribble past 5 players and his main passing option will be another old, slow, short player Aguero who will wait the ball in the middle.
It will probably work to some extent against Getafe/Levante, but in a CL, we'll probably lose 0:4 without real shots on goal since our attackers will be one year older and our attacking play will be even more predictable/one dimensional than today, aka= give the ball to Messi and he will either dribble past 4 players or pass to Aguero.
How hard is to predict those moves and defend against it?
Roma 0:3
Liverpool 0:4
Bayern 2:8
Psg 1:4
= will give a hint
We are trying to score in the same way all the time, yet we concede from possession, counters, crosses, headers, corners, longshots.
On the other hand, if we accept right away that we suck in a CL and that our only goal is La Liga (which means making Messi happy and hoping that he will single-handadly lead us to a title), then fine = let's buy his friend, let's make him happy and hope for the best (final La liga title).
Uefa Super League whipping boys here we come. But atleast we got the Messi franchise intact until he is 38.