He could keep playing his free, roaming role, which usually is around the #10 position, and keep arriving late and score some goals.
He obviously can't play as Xavi, and he shouldn't really play any position but be free (the problem is when both the wingers and the interiors play almost free roles as well)
The question becomes, should he have three midfield types behind him, and how many attackers in front of him? Should Barcelona play with two players on each flank or just one?
For a long time he lacked forward runs in front of him, then he lacked people behind him, and then he had two, three, four players contesting the same space as him...
I believe with Busi, Puig and Thiago behind him, a decent striker in front of him, Alba on the left and someone on the right, he can find a perfect role for quite a few years more, if he's happy.
The way he has played last year, he really should change club in order to get some new spark... I don't want to even begin to criticize Messi, but it doesn't work so well at the moment, regardless of surroundings.