I'd rather see the Hawks associated with the Justice Society, maybe in a flashback/flash forward or one based on Justice League of America #21 & #22.
Just for the sake of speculation, what if Hawkwoman (as Shayera had been called since the 80s, which I don't think Brad Bird would known of the name change) appears far a space-based arc with Katar getting a mention while the Carter Hall version of Hawkman appears in the JSA team-up?
And it would a great lose ITTL to lose Phil LaMarr as John Stewart.
I chose Joe Morton as a placeholder for the most part as LaMarr was still limited to a few guest spots on television and didn't get his big break until
Pulp Fiction in 1994. It's still possible that he auditioned. I met the man at the Calgary Expo twice, and he was a quite knowledgeable about the comics so I wouldn't count him out completely.
Here are some more suggestions for casting...
Charlie Schlatter as Wally West/The Flash - He was the original voice for the character in
S:TAS and this would be him coming off the role of Ferris Bueller from the doomed television series.
Anthony Geary as Green Arrow - A bit of stunt casting on my part. Kin Shriner (AKA Scott Baldwin on
General Hospital) voiced the role on
Justice League Unlimited OTL, I thought why not cast his
GH rival in the role TTL?
Rosalind Chao as Shayera Thal/Hawkwoman - I thought it would fit given the role she plays on TTL's
Star Trek: TNG.
Julie Brown as Zatanna - Because Paul Dini says so.
Speaking of whom...
Jeffrey Combs as The Question - Maybe not on
Justice League, but on TTL's
Batman: The Animated Series as a stand-in for the Spirit since the two are visually similar. It would be waste not to have Combs as the character.