If they ever did a squeal to “The Dark Knight Rises”, I think they should call it “The Dark Knight Returns” and the villain should be a much darker version of either The Riddler or The Penguin, without actually naming them. I prefer the Riddler, his use of logic rivals that of the Batman with a sadistic twist. He should be some public figure rising to office while taunting Bruce Wayne with his riddles.
Good Title.
It could be two part animated where Batman teams up with a young female Robin and fights mutants and the Joker 
As long as Christian Bale isn’t involved, it all sounds good to me.
OB
I think someone like Hush would be better. I see too many ways Riddler might just seem to be a cut-rate Joker. Penguin would be a lot like Falcone and Clayface wouldn’t really fit in the Nolan style Batman stuff without a drastic change.
That being said, I think the Nolan/Bale Batman movies have pretty much run their course.
Oddball - I like the title, but I am not tied to it. I had no idea there was a animated movie on it]
Starsaber - With Bruce Wayne still alive, I think it is possible to return him. I like the points you made about the penguin and Clayface, But I disagree on The Riddler.
The Joker was the complete antitheses to batman, The Riddler seems like a perversion, A case of logic gone wrong. To me this is the one type of enemy that has not been explored
When you put it that way, it makes a certain amount of sense, but the last issue of Hush was the only time I took Riddler seriously. Maybe I haven’t seen the right material for him to be a believable villain. My opinion of him is pretty much shaped by the Adam West Batman series. 
EDIT: While no Jason Todd Robin means they couldn’t do an exact copy, someone along the lines of Red Hood who thinks Batman is too soft on criminals could work too. Someone who sees himself as a hero vigilante like Batman, but is willing (and quick) to kill criminals rather than wrap them up for the cops.