I'd really like to see The Riddler. I don't think he'd been a "green Joker." I doubt whoever plays him (Eddie Murphy lol come on) will be as good as Heath but there's lots of potential. I'd love to see The Riddler leading Batman into traps, almost making it seem like he's on Batman's side since he is now against the cops and making the cops think he's against Batman but he's really on no ones side, just trying to cause chaos.
Fuck, that almost sounds like The Joker-lite.
Robin heel turn? I really don't know. I like some of the ideas in this thread though. I guess we'll have to wait and see.