Dammit, I made a thread about this, but I didn't see this one was already made. Oh well, I'll just copy and paste what I posted over there
It seems like at some point in the story Nightwing and Cyborg will switch sides and leave the Insurgency to join the Regime. I wonder what could have happened to spark that, although I have two theories.
1.) I remember hearing in an article somewhere that some of the other Titans will make an appearance in the story mode at some point. I think it's possible that somewhere in story mode some great tragedy happens to a close friend of theirs', like Beast Boy or Starfire, and it causes Nightwing and Cyborg (and maybe even Raven) to join the Regime to take a harder stance on the villains/criminals that killed their allies.
2.) I think it might also be possible that Batman gets very desperate to defeat Superman's Regime to the point of accepting the aid of villains. So maybe Batman allies himself with Deahtstroke and when the rest of the Titans find out they are outraged that Batman would do such a thing, and decide to leave the Insurgency because of it.
I really can't see Flash in the Regime, he has to be a double agent or something for Batman.
Flash is the classic "believes in the ideal until things go horribly wrong and switches sides" character in this story. This pretty much applies to Aquaman as well but it's difficult for regular joes to relate to an underwater prince/king/god or whatever Aquaman is in the Injustice storyline.