I'm all for allowing wealthy owners to pump big sums of money into football and the PL. City and Chelsea have, recently, brought world class players to the PL which increases the quality of PL football.
I think to protect the long term competitiveness of the game the PL should consider a salary cap structure along the lines of the MBA and NFL. This could keep the playing field somewhat even and protect to become a 2 team league like the Spanish league.
The PL is already turning into a 2 or 3 team league with Man U, Chelsea and City ahead of the rest of the teams, but if each team can spend the same on wages there is a limit to the players they could bring in unless these player will play for lesser wages.
To have financial fair play rules in place and not enforce them only creates confusion. I would think a salary cap might be easier to enforce and working models of this system exist so it won't be like re-inventing the wheel.