The thing about Captain Triumph is that he first appeared in Crack Comics #27 (cover-dated January 1943 and published in November 1942), but I don't think Roy Thomas ever got that far in the stories.
Aside from a picture of him practically hidden on the cover of All-Star Squadron #1,
I don't know if he ever made it into the stories.
There were a couple of Who's Who in the DC Universe entries that had him as a member:
from Who's Who: The Definitive Directory of the DC Universe Vol. XXVI (April 1987)
from Who's Who Update '87 #1 (August 1987)
^^^Yup, I Googled all the same sites you just did!
I simply want him on the team.
Somebody on another thread suggested Bob Hope. His comic started in 1950, just enough time to be in the original team.
I wouldn't mind having Airwave on the team. Not the kid version who was just rescued in the Stargirl series, but the older one with the updated blue and yellow costume who helped Hal Jordan out in the Morrison GL series. He was a backup/reserve member back in the last JSA heyday run.
My other choice would be Jonni Thunder. Similar setup to Jakeem but different enough to not feel redundant. Plus, the idea of a tough-as-nails plainclothes PI hanging out with a bunch of brightly-costumed characters appeals to me. I don't always love it, but every once in a while I like seeing someone just wearing a suit or something set amongst all the spandex, but as an equal member, not a support character.
Yeah, I wasn't 100% sure how that worked. Most other kids' lives stopped when they were taken, but in Airwave's case it would mean the events of the Stargirl mini would have already occurred/been resolved years before he had his adventure with Hal (from his perspective), which was chronologically presented prior to the mini's events (at least from Stargirl's perspective).
Or, you know, the multiverse rebooted eight or nine times between the two stories.
^^^I thought I remembered Airwave actually related to Hal.
Googled it and yeah, they’re cousins!
https://www.cbr.com/green-lantern-annual-air-wave/
Not sure if I’m telling you something you already know, but you didn’t mention it so I figured I’d bring it up.
DC character: Tom Strong would an interesting choice but so would Elijah Snow
Non DC: Captain America hands down but somewhere in the multiverse he’s probably a member 😝
Be yourself everyone is taken !! I'm an X-Man trapped in the DC omniverse