I think a modern revival of All-Star Squadron would be a great idea for a maxi-series in the vein of the recent Mister Miracle maxi.
As much as I like the original members, I'd like for them to focus on a mix of old and new Golden Agers. Let's see the beginnings of Amazing Man's career, but I also want to see what the rest of the African-American mystery man community was like. Immortal Men crashed and burned before the first issue even came out, but I love the idea of the Harlem Crimson Avenger type. I would love to see the origins of young John Henry from New Frontier.
And I think the concept of a newly created closeted member of ASS (snicker) is too good to pass up. Man or woman. I don't care. I think there's lots of potentially cool stuff to explore there, particularly as it relates to the other members of the Justice Society. Given Alan Scott's discomfort with his yet to be born son's homosexuality, would he be in on the secret or would he be blissfully oblivious like so many were about guys like Liberace?
In addition to Alan, Jay Garrick is a must. These two simply represent the Golden Age of DC comics to me. Carter transcends generations now. Jay & Alan are the two greatest avatars of this era.
Tsunami should be there to represent the Young All-Stars and the generally unexplored Japanese internment angle. You could also retroactively explore long-lived characters like I-Ching, his evil twin All-Yang (who first appeared on the cover of Detective Comics in 1937), Ra's Al Ghul, and that time's Brother Blood.
1940s DC is a ripe period for exploration. I would love to see them do more with it once they return from Limbo for the third time