Messi is a grown ass man, not a spoiled brat. No way he'd make such demands just to play with his buddies. That's the kind of behavior I'd have a hard time expecting from Neymar, let alone Messi.
And honestly, if Messi wants to run the team into the ground to get his buddies in, he can fuck right off. Ship his ass off to Man City for 300m and let them deal with his demands. Use the money to rebuild the team with players who are actually there to help the team win trophies instead of partying with their buddies.
Before y'all jump on me: That was a completely hypothetical scenario in which Messi is basically the opposite of his real self. My comments were towards the hypothetical spoiled brat Messi, not the actual Messi.
Short answer: No, I would not accept this signing, even if Messi demanded it (which he wouldn't). If he demanded it, that means he's unprofessional and his priorities are in the wrong place and he needs to GTFO. All three of which are false statements. Messi would never, EVER make such childish demands. And anyone who does so has no place at Barca or any top club for that matter, no matter how talented they are.
Still, wouldn't be surprised to see Farto and his media mouthpieces claim that Messi asked for Di Maria. Conspiracy theory time: we actually aren't interested in Di Maria at all, it's BS they're spreading that they plan to use to defend themselves if Messi leaves. "See, Messi demanded that we sign Di Maria. No player is bigger than the club, etc, etc." If Messi refuses to sign a new contract, I wouldn't be surprised to see MD say it's because we didn't buy Di Maria.