Revenues from ads and sales of his jerseys? Wasn't not the same Barca that ran into debts because of the lucrative offer they gave to him in other to tie him down? I take this news to be nothing but speculation. Messi's era has come and gone and Barca has no desire to bring him back to Nou camp. They already have a young talented squad that can compete for major trophies in Spain and europe.
I see no point in bringing Messi back as a player. He's old, slow, and maybe unable to compete in La Liga. The better to see it as a different view. They can give him as position in the club to increase club's engagement. We know how big his fanbase compared to any players on their squad now.
If we're talking about revenue from sales or something else, it totally makes sense consider he has biggest fan base after Ronaldo. Having him will also boost the revenue by the club as it's bringing back the old days of him on his former club.
Ambassador? Director? or another position? it's all good. I remind you even though he's not barcelona's player, but he's still remain iconic to the all of barcelona fans.