any reasons why you didnt list cartoons from japan? or china for that matter? i think naruto and one piece would make a great cartoon based AA/AC game ^ they are the biggest thing in japan at the moment, so they have to be good... otherwise they wouldnt be the biggest
heck, you could throw in sword art online too (another massively popular book turned cartoon)
Rocksteady isn't a Japanese company and established American IP are more flexible to having original storylines. would you want these games to recreate the manga/anime story or have its own?
i don't like AA but i love AC. an open world Naruto or One Piece would have to be massive. and i would imagine they would be even worse if they were contained in a single location like AA.
also both of those have such an ensemble cast, it would be hard to please fans just playing the main character.