Big obstacle preventing Messi returning to Barca

Leo Messi is the main name this transfer window for Barcelona. The club want him back at the Camp Nou once his contract ends with PSG in June. But, in order for that to happen, they need to free up some wage bill and sell players.
Barcelona have already supposedly presented La Liga with a plan which explains their plans to get rid of key players. According to 'Sport', the only problem is that there are lot of players who don't want to leave.
The club would be willing to listen to offers for Ferran Torres, Jordi Alba, Ansu Fati and Kessie. All of them are on the way out, but there are also others who could also come in if those refuse to pack their bags. In that case, they'd think about letting Eric Garcia or Raphinha go if they'd get the necessary cash to spend on signings.
It'll be difficult for Barca with Ferran Torres, Jordi Alba, Ansu Fati and Kessie. None of those players, according to the Catalan newspaper, would be up for going, and they've already told the club that.
The club know that getting players out will be tough. From the end of May, when the season ends, that'll be when the club try and sort it all out.
If none of the four mentioned players accept leaving, Raphinha could be the one to help out. He's got good links in the Premier League and selling him would get in a good bit of money. In Eric Garcia's case, they'd only let him go if they got an offer that was too good to refuse.