Leader - Superman (Electric version, blue suit with lightning bolt insignia...)
2IC - ION (Kyle Rayner)
Parallax - (Hal Jorden when fighting for redemption)
John Constantine - (For mystical backup, kyptonions and energy beings seem to have a problem with magic. The constantine from the comics, not the lame ass movie)
Jesse Quick - (standard speedster on team, for those who don't know she also has flight and superstrength powers, not just her speedster powers)
Nightwing - Dark member of the team (for some reason i can see Nightwing and Constantine getting on really well lol)
Jade - energy powers as well as untapped plant powers
Hitman - (Thomas "Tommy" Monaghan) for the fight's that have to ended with a deadly outcome.
Lady Flash - (Christina Alexandrova) for speedster backup when Jesse is unavailable. she maybe a bit borderline, but i'm sure she would be stable working in a JL type environment.
Powergirl - (Kara or Karen Starr) Powerhouse of the team, kryptonion based strength and other powers (sorry, i know power girl from pre crisis on infinite earths, not too sure of her new backstory after the latest crisis)
Supergirl - Kara Zor-El (kryptonion backup for Powergirl and Superman)
that's my team... think it's quite well rounded with everything a JL team needs lol
and for backup...
Back - Supergirl (Goldenage, Kara El), Powergirl, Wonder Woman, Supergirl II (Kara Zor-El)
Front - Jade, Saturn Girl, Strange Visitor, Engineer, Black Canary I, Batgirl I, Zatanna, Jenny Sparks, Lady Flash