I suggest you make a list of characters who should join it and fit the I guess 'theme' of the group and get together with those players for an arc that would make Bats form them. Because so far in this RPG, from what I've seen, he's pretty much a loner and would have to be forced into making a group.
It might be kinda hard for Batman since he has the whole no kill thing and Logan..well...it's Logan...

But it would make for great stories.
*Edit
HOWEVER this is a ONE univers RPG meaning here...Batman might not start the Outsiders. Batman seems more suited for the JLA, or whatever we name it, than the Outsiders, I was basically comeing up with an idea for the players of the line walking characters.