There is a reason there is an AO title, and I beleive companies should allow AO titles on there systems. I do however believe that many M games are already pushing into that category so an AO would be ridiculous.
Edit: I do also beleive the world isn't quite ready as gamers are. We would have lawers coming down on games like an executioners axe.
CURRENTLY PLAYING: Warframe, Witcher 2