My Justice League line-up. These are traditional characters unless noted.
Brainiac.
Intelligence based. The idea would be to bring back content from a story by Marv Wolfman where Brainiac was actually on the lawful/order side of things until a situation arose where the chaos version of Brainiac was needed and Superman enabled this transformation back away from lawful/order to chaos. Always thought that was a brilliant Superman story that fit even better than the Batman is responsible for Joker themes. I'm not sure of the details yet but that story would be explored and Brainiac reverted back to lawful/order but there would be mystery surrounding him and distrust from some of his other members. Is that other self gone or lurking within Brainiac self-conscious. It could end up either way with him remaining on the side of lawful/order or to chaos. Unknown.
Power Girl.
Filling the Superman archetype. It's a potential that she's the one who restored Brainiac back and there's a interpersonal subtext between Power Girl and Brainiac substituting as it would be for Superman. I'd want to see Power Girl not in a typical over masculine portrayal where she always has a mean face and at every turn the narration tries to tell you how strong and tough she is, but instead a balance of feminine/masculine. And i'd like to see brought back a wide variety of tools for the Super character like how it used to be where Supergirl or Superman would use their super intelligence to do something, not just the brute muscle of the team. All-around Super. An uncertain obstacle at the moment in how not to make her too powerful if that were the case. Would probably have to do some cliche thing like she hasn't learned her powers yet. Cliche but it usually works unless can come up with a better idea.
John Constantine with Etrigan
Filling a supernatural + witty banter + Detective role. Something along the lines of Etrigan was helping Constantine search for something in Hell but things went bad and it's revealed that Constantine is betraying one of the big bad demons who catches him and after Constantine unsuccessfully talks his way out of it, the big bad demon curses Constantine with being responsible for Jason Blood's life to where only Constantine can sooth the Etrigan demon for Jason Blood. The big bad demon's revenge. This would cause various comedic situations involving the two of them and a love/hate kind of relationship journey.
Max Mercury and Jesse Quick.
Taking up the typical Flash speedster role. Max will be mentoring Jesse who will fill the archetype teenage role. Some inspiration for the character from the motion picture series. Coming of age type journey.
John Stewart.
Filling the Green Lantern. Even though there isn't a spoken leader he would sort of be the unspoken leader. Strong/silent. Unwavering in his conviction and extremely formidable with the Lantern ring. He will quickly gain the reverence of the others when they first come together and light the way as their beacon of hope even at the worst of times.