I BELIEVE IN KRISTIN KREUK
And I agree with what the threadstarter said about skipping Barbara and putting Cassie. Not everything has to follow Canon comic continuity. In fact, in Nolan's world it probably makes more sense to use a Cassie since she has ties with the League of Shadows and Barbara is seemingly still a baby. As awful as Street Fighter will be, the one thing Im hoping it will salvage is to show Kristin in full battle mode. Physique wise, its not big a deal. Cassie is a young teen-early 20s girl and K is that too. And here ethnicity is dead on, so make it happen!
I know some naysaysers, will look at her work as Lana Lang in Smallville but lets be honest, that was the writers fault. When it comes to young actors there only as good as the director and the writer of the character. And dont bring up Rachel Dawes because Cassandra Cain by default is no Rachel Dawes and would bear more relevancy if they included her compared to Rachel.
As for Robin? I have no clue. Before Nolan even decided to go with a restart, I thought about maybe using Jake Gylenhall and or Joesph Gordon Levitt. But that was 6 years ago and a lot has changed since then. I would say this, If they do think about including him in Nolan's world, I think I would make him a bit older than 9 years old (which I believe in Canon is when he became Robin), I would probably cast someone late teens/early to mid 20s who could pass of for 16-18 years old. Realistically I dont think Bruce is gonna take a child in and teach him the League of Shadows ways. So its gotta be a young dude who was roughly his age when he travelled the world. As I said I dont know who to cast. Im gonna go a little left field and say maybe Emile Hirsch (Into the Wild) cause I think he has good actor potential. But Im really open to a better suggestion.
Having said all that, I dont think we're gonna see any additional members in this franchise. I gotta a love for the Bat family as a whole especially in the books and in both animated series but it just wouldnt work.
You know what I would like to see though? A spin off either as an animated series (straight to DVD, or TV show. Mo-Cap?). I guess a live action TV show would be a bit like BoP with the Bat family that spins off after Nolan's franchise and focuses on the rest of Gotham (Imagine if Batman went away for a while). But who the hell wants to see that?
I could sort of seeing them being introduce as just Cassie and Dick in training and then leave it as an opening that they become Batgirl and Robin when the series ends (this is all if the franchise goes beyond a trilogy). It seems somewhat plausible because the impression Im getting from TDK is that Batman surely will inspire people to follow either him or the Joker because "case of the theatrics" and "dramatic examples of empathy" are whats in no?
But again, it probably wont happen but it would be cool if it did.