The whole rating system has had such a tumultuous past. The rules are ambiguous and way too subjective. I've heard of so many stories from directors of how they "manipulate" the ratings review process to get the rating they want or how they had to change small details to suit the reviewers. I mean, seriously, how can even just the use or repeated use of a word increase your rating, yet mild violence won't. Of course sexual content should be rated but it should be based on what is age appropriate for the type of film.
Grrr, sorry, I just had to vent. It just annoys me when a few individual opinions are allowed to have an impact on the majority.
Anyway, I'm all for the way Fox has done this. It should be up to me to choose what I want to see but for children I'm not sure how you would go about it. Parents in general are seemingly reluctant to do much and the theatres don't seem to enforce the ratings anyway.