Personally I think they should add some sonic characters. I know its a third party game but still they have some cool characters. Like Amy rose could be a new female character because i don't think adding rosalina is going to cut it. Also she is the most liked female character for that series. Besides Amy they could add shadow. I know to some of you he is just the black and red version of sonic but he could have some cool chaos attacks. And let's not forget about sonics faithful side-kick tails.