I think if they're going to do a Robin, they should do his origin more or less. Maybe do a "prequel" where Bruce Wayne has a young, nearly teenage Dick Grayson living with him. There could be a flashback that shows how Bruce rescues a younger Grayson from the loss of his parents and one of the focuses could be how Bruce tries hiding his identity from his metaphoric son who lives with him. There is a great story to be told paralleling Bruce's childhood with Dick's. Then, when Batman's identity is made known to Dick, Dick seems to be interested in following in Bruce's footsteps, looking for revenge and a thirst for violence. Bruce tries to keep Dick away from that, but Dick somehow gets his hands on a Robin suit. It would cool to have Robin save Batman, but in no way should he out there fighting and beating anyone up really. Just a nice little scene where he rescues Batman, but then Batman has to protect him for the rest of the movie. Finally, show that Dick isn't like Bruce and when push comes to shove, he is not as dark as Batman, maybe even have him forgive his parents' killer in the end (assuming that he'd be a minor character at least).
I think there's potential with Robin, in any event.