3) Robin
While I would love The Batman to revolve around the return of Jason Todd as the Red Hood, it doesn’t appear as if that’s the plan as of right now. After all, Deathstroke never played a role in the comic book version of that story and there’s been absolutely no mention of Jared Leto’s Joker showing up here (which would be a necessity).
If the storyline is somehow adapted, I could live with a flashback featuring Robin, but one thing this movie shouldn’t do is introduce us to a new version of Batman’s sidekick. Whether it’s Carrie Kelley or Tim Drake, Robin doesn’t need to show up.
It would definitely be nice to get some insight into the Robin costume Batman has on display in the Batcave though, but that would be best achieved by having someone like Nightwing appear. A former Robin, Dick Grayson could now be estranged from the Dark Knight due to what happened to Jason, and even just a simple conversation between these two could help set the stage for the Red Hood to appear down the line.
Ultimately though, it may be best for Batman to have no help as there’s something quite a bit more exciting about him heading into battle with no back up.