New Troll said:
They already have a rating for what you're describing. Ao which stands for "Adults Only" and is for ages 18+.
Problem is, they effectively don't have such a rating at all since stores simply refuse to stock AO titles, with the extension that major companies refuse to make them. AO is such a death sentence that Rockstar re-released GTA: SA to remove content that wasn't actually in the game just so it wouldn't have the AO sticker on it.
I believe what he's talking about is an AO rating which doesn't have the same pariah status and which games are actually released in. 'Adults only' makes it sound like hardcore pornography, 'Mature' makes it sound like something for older people.