For me, this is our best lineup:

Ansu Fati

O. Dembele P. Coutinho L. Messi

F. De Jong M. Pjanic

J. Alba C. Lenglet G. Pique S. Dest

Fati - A pure centre forward, he has foot work to take on defenders side ways and in the middle when through on goal, he also has shot accuracy and is lethal in front of goal.
Messi - For me he should be on the right wing, drop a little, just a little to receive the ball +

... and make a run. This will make him more productive as his runs can lead to fouls and also disorganize the opposition defence with his dribbling and through balls, he doesn't need to be in the middle as teams always focus on him and will lock him up easily in the middle. +

Ousmane Dembele - For me, he should play on the left wing, his pace, dribbling and runs create space for other attackers and also stretch the opposition defence leaving spaces in between for Playmakers to feed in through balls, he should do most of the dirty work.

Leave your thoughts about this thread in the comments section, let me know what you think about my lineup.