That rule will kill Italian football even more. Not only do many Italian players suck these days but this league is in some serious need of some international superstars. Also, some teams like Udinese live and run their business through their international players.
The quality of the league go down when you have to use force some lame Italians into your team who's quality really belongs in Serie B. Sure if every European league had these same rules but there is no need to make it harder on yourself.
How will that rule even work? What if you don't have 4 Italians, what if 3 of them are injured? Are you suppose to bench a much better player like Asamoah to start Marrone or Padoin?