Don't wanna defend Fisher because he is a giant asshat and a perennial loser but with the rules as they stand it's certainly true that the refs have unfortunately too much leeway when it comes to PI calls. And making that reviewable is opening a can of worms.
Now, that being said the easiest solution to this problem is not what the NFL is proposing and just carrying on with something that is clearly broken but instead rework the rulebook to be something that makes it possible for games that are officiated by different refs to still be consistent in terms of rulings.
If this means that things become even more drastic in terms of contact or they decide to go the other way and allow more contact I don't really care about. But for ****s sake lets have some consistency. Because ultimately the only thing that's worse than one of those soft DPI calls is if its only called on one team and the other gets away with it.