Yeah. I think a sorta justice renegade squad mugh be a cool idea to go with. Or maybe during a search and rescue, the said characters hear something happening in a city, and they all have that same pull to go do something? Then as we go I suppose we could expand upon it.
I dunno, I could always help you work with the numbers and if you want to keep it small make the decision of cutting people to keep it small. It has to work with whatever you're comfortable with dude. As CS flow in sometimes it take a chemistry for the party to run smoothly.
These are all just suggestions though, please don't think of me trying to shove things down your throat or whatever. ;-;