I think DC needs to go with one more JL book....Justice League of America could be more of a street team, headed up by Vixen and Black Canary. Dinah would bring along Green Arrow, which would provide a real strong core.
To continue with a more "classic" vibe, you could also have Firestorm and the Atom....Firestorm would provide power, but not TOO much (just enough for a more down to earth oriented team!), while Atom is a Legacy character, but one that can still be greatly developed.
I also thought Huntress might be fun....a more athletic, spy-trained one, so there wouldn't be two heroes firing arrows....but on second thought, I thought it would be wiser for a street team to have a A) telepath/someone with mental powers, and B) someone with morphing powers/ the ability to disguise themselves.
Now, Martian Manhunter would be perfect for both those reasons, but I think he's going to be too busy with the main book, so let's think outside the box for these last two!
For the telepath, let's bring in Lilith from the Titans, and for the morpher/disguise artist, let's add Black Orchid to the team! Number of bonuses here...two characters that can still be greatly developed, and it would allow for a female majority, a rarity in comics!
So... the street level Justice League of America team would be:
Vixen
Black Canary
Green Arrow
Firestorm
Atom
Omen
Black Orchid