Fuck yeah to Booster Gold and Blue Beetle. As much as I love Power Girl, I don't want to see any other kryptonians, simply because I think they'd be too similar to Superman. I keep hearing everyone want Zod included, but if he is, I'd just want him to be a skin and voice pack for Superman and not a real character (evil supes even already tells people to kneel, so why do we need him?).
As overcrowded as the bat family already is, I actually would like Red Hood. We need some more villains, and I have a hard time coming up with some that aren't from Batman. Maybe Larfleeze? Bizarro would make a good 'big' character like Bane or Doomsday. Deadshot... is probably too much like Deathstroke. Darkseid? Eh, doesn't really fit, and he's already a stage transition.