Well, taking Superman or Superboy would be complicated, as Superman disappeared in this games timeline, but he is set to return. I was possibly going to be playing Superman when he did come up, but I'd be a-okay with giving up that role, as I'm already planning on playing Green Arrow and Red Hood. We also already have Power Girl, so another Superboy/Supergirl would be rather unnecessary in my opinion, but I'd love to hear some other people's input on thiss.
In regards to a male Batman sidekick, I think Lois was saying she already found a Nightwing. Robin in this game is Bruce's Daughter, going by Nina Wayne in here as opposed to Helena Wayne.
I'll have to talk to Lois regarding Nightwing, though. If she didn't find one, that may be a role you can fill. And of course if anyone else comes to mind you'll most likely be able to play it. The DC Universe has a vast collection of heroes, after all.