Ffp was built so that it effectively is impossible for mobility. They effectively established a top 6 in England and have made it next to impossible for other teams to come in(Leicester fluke aside). The big clubs generate enough revenue and will always cook the books enough to be exempt from Ffp. It should have been done in 1993, not 2013.
If a club does come in you just get 6 bayern Munich type teams ready to take their best players(see Chelsea with Leicester e.g.)