You honestly think If Messi says I want to play in the Premier League and dont mind if its at City or United...we both wouldn't fight for his signature?
Between Mata, Lingard and Sanchez im sure you can pay for a Messi.
I'm not saying that his wages can't be paid, I'm saying if in some alternate universe that happens it might not be worth it.
I really enjoy watching Messi play, I have flown to Barcelona a few times to watch Barca play and I've watched pretty much all of Barcas games since 2006 when Ronaldinho still at the peak of his powers.
I see United as a young squad now and I see players like Rashford, Martial, Greenwood all wanting to take the ball and take responsibility they are at a key stage in their development. I'd much rather take a 20-21 year old that's pretty much world class at £120-130M than take Messi.
Messi is Messi yes, but I'd much rather spend those wages on 2-3 additions across the squad that make the team better.
You also risk warping your whole wage structure with players like Messi, 'Oh Messi is on 500,000 a week then I'd like 250,000' when without Messi that player wouldn't even dream of asking for 150,000.
Again for me Messi is the GOAT, he's truly phenomenal but at this stage I wouldn't want him in the United squad because I'd much rather have the team we have now to develop together over the next season or so, and keep the core of the team together.
I don't honestly see Messi coming to the premier league now, it would be Italy, or retire at Barca.
I think though Messi should leave Barca, he's not going to win much there in his twilight years with the Barca board being as bad as it is.