I am not completely sure what will be happening after Trinity War but one of the teaser images showed Batman and Superman fighting. Therefore, it is possible that they will become rivals after the event and that Batman will form a new team of Outsiders. This is my list of who I would like to be on that team:
I would definitely have him as the leader of the group, after leaving the Justice League, he would decide that they need closer monitoring and would set up his own team to do that and more black-ops type missions.
I would include Wonder Woman because I am a big fan of the Batman-Wonder Woman pairing over the Superman-Wonder Woman pairing. Plus, I think that having two original members on the team would give it more weight.
I think that the best super teams in the DC universe have a Green Lantern on the roster and Stewart has to be my favourite because of his role on the Justice League animated series. Plus, he already had a fairly close friendship with Batman pre-New 52.
He has been one of my favourite street-level characters (almost on a level with Batman) ever since I read Black Lightning: Year One. I am not sure of how he is in the New 52 yet but I think that he could bring some cool powers to the team.
I don't think that he has appeared in the New 52 yet so the Outsiders could be the perfect way to introduce him. He would be interesting because of his ties to the Markovian royalty.
I included Nightwing because he is one of the only Bat-family members that hasn't been tied to any real team in the New 52. Plus, the fact that he was Bruce Wayne's ward was retconned so this team could re-enforce their friendship.
Being totally honest, I dislike what DC are currently doing with Huntress. I don't find Wayne to be nearly as interesting as Bertenelli because she came from a mob family but still turned out to be a hero, coping with a desire to kill criminals. However Wayne is the daughter of Batman so heroism is expected. I don't think that Bertenelli is dead (an event which is referenced in World's Finest #1) probably just in hiding from the mob.
Finally, I would have the Outsiders be Cassandra Cain's New 52 debut. She is one of my favourite Bat-family members and I think that she would fit in very well with the Outsiders.
