That Hawkgirl is almost completely a new entity, no?
It's the Silver/Bronze Age Hawkgirl - detective from Thanagar and so forth, using the Englehart strong characterization, and a few things unique to this animated version, like the "lightsaber" space-mace, the light Spanish accent, and the lack of Hawkman, museum job, and Absorbascon. There are elements of HAWKWORLD, such as Thanagarian militancy, and the fact Hawkgirl came to earth as a spy (though used with much greater effect).
The strong, breakout characters on the show --I've seen about 1/6 of the series in one form or another-- were basically nobodies/ciphers in the mainstream DC Comics.
Well...that depends on your definition of who would qualify as a "nobody/cypher." Some of the stronger episodes with stories told based on a single character were Green Arrow and Booster Gold, for instance...I doubt they'd qualify as B-listers. Though a character as esoteric as King Faraday doing a guest-shot was pretty unexpected, I must say.
Jack Kirby had a bigger influence on the series. More of the characters and themes he first introduced/created were spotlighted than any other comics creator I can think of. Maybe Siegel/Shuster.
Here's the thing: Jack Kirby never did a run on JLA comics. I don't think it's reasonable to count Kirby as an influence on a book he didn't really help shape.
I don't deny somebody as ubiquitous as the King would certainly have some influence in a Godfather-esque sense on any show about superheroes, however, among the seven principle characters originally selected for the show, the two idiosyncratic and less obvious choices were characters that Englehart wrote (and the show creators used the Englehart characterization), with Hawkgirl being a character he brought on the team and made a tough cookie, and John Stewart being a character that Englehart worked to establish as a character when others would have done stories with Hal.
Denny O'Neil and Dick Dillin created the JLA Sattellite, not Englehart, but this was the time that Englehart wrote his stories, so it's apparent they've got that time period on the brain, for instance.
Don't get me wrong, Kirby's concepts certainly were influential (the presence of the Fourth World stuff, for instance, or the Demon in a lot of episodes) but not any specific, individual story, even in a vague, reworked way. Note I didn't mention Englehart's LEGENDS OF THE DC UNIVERSE issues; the episode that was loosely adapted from it was in fact so loose I'm not sure it qualifies as having Englehart as prime visionary). If we had the Leaguers team up with Orion and Lightray to blast the Deep Six, okay, you may be right.