This notion that you can be so rich nobody can compete with you is in footballing terms, not really true at all. With or without FFP. You can only have 25 players in a squad, and you can only field XI. You might buy 11 of the most expensive players in the world, you might have the highest wage bill in the league as well, but it won't guarantee you success. So when people talk about it being unfair that owner X is this rich or owner Y is that rich, it's actually nonsense.
The truth of the matter is that whether it's FSG or Kroenke or the Glazers, they can all use their own wealth and match City pound for pound in our transfer spending. Regardless of how 'rich' Mansour is reported to be.