Even though you're probably going to put me back on ignore, I still love ya mate. Never had any hard feelings against you.
GivenI don't get La Liga games anymore, Barca predominantly plays a 4-3-3. I get you are a Messi fanboy and that's totally fine, he ain't surpassing Pedri, Busquets, or de Jong in that formation. That means, bringing him back for Xavi is actually a negative for Barca and I argue makes you lot worse.
@bluesfan94 did mention playing him as an RW and even though I think he would do well enough there due to his experience, he isn't currently better than Dembele, Gavi, or Torres (when Dembele gets his half-of-a-season groin pull injury lol, then he could challenge as a starter). Nonetheless, he has a lot of baggage and I am not he has the agility or speed required for a winger role. Not strictly talking about offence here, but the heavy requirement to track back on the defence as well. The only way bringing Messi back works is by going back to a 4-2-3-1 or 4-3-2-1 formation and I doubt Xavi would do that.