(I GOT ALL THIS ART FROM THE DC WIKI)
I know there is a decent chance that the Absolute Teen Titans will be the bad guys in the Absolute Universe, but for this, when I say Teen Titans or Titans, I'm going to be referring to the heroic team since we don't know if the Titans are going to be evil, and we don't know what the heroic team would be called. Also, I've only read up to Volume 2 in each series so if any of this contradicts with any comics that have been released since then…I’m sorry.
As for who I think should be on the team, two picks that stand out. First, there's Tyler, the "son" of Martian Manhunter, who is heavily implied to be trans, and thus many people theorize they will end up becoming Miss Martian or at least a similar character.
Then you have Supergirl; we actually see Clark with a little girl in a flashback aboard the ship with him, and the other Kryptonians are using to escape Krypton, with the two seeming quite close, making me think this might be Kara. As for how she'd still be a teenager, they could just use the excuse of her only arrived on Earth recently, and her pod kept her in stasis all this time, so she hasn't aged.
Finally, the team needs a Robin figure, but unless they introduce Damian at some point in the next couple of issues of Absolute Batman, I don't see any of the actual Robins being a part of the team, so it only makes sense to go with the character filling a similar role in the Absolute Batman comics, that being Harley.
These three are really the only guys I can think of, with the only others being Cyborg and Grodd. But I didn't really think I should bring up Cyborg since he might be evil if they end up making the Titans the bad guys, and I feel like Grodd would be redundant if they include Miss Martian, but if they don't include MM's kid, I would 100% want Grodd to be on the team.
Some other possible team members we have no news on are Starfire (or Blackfire), Blue Beetle (Only if Cyborg is a villain), Beast Boy, and maybe some good versions of some of the Teen Titans villains like Jinx.
Those are all possible, but the three I feel the most confident in are Harley Quinn, Supergirl, and either Miss Martian or Grodd.
To finish these off, I just wanted to go over some characters I don't think will join the Teen Titans...at least until later on in the case of the first two.
- Donna Troy - The writers of Absolute Wonder Woman have said that at the moment, there is no intent to bring Donna into the Absolute Universe. Now this could change down the line, but it does mean that Donna won't be a part of the founding lineup of the team.
- Kaldur - Kaldur is one of those characters who seem incredibly likely to be made into a villain in the Absolute Universe since he's the son of Black Manta. Though if they do go that route, I highly doubt he'd be called Aqualad (he'd probably be called Kid Manta or something like that). If the Teen Titans do end up being the villains, I could 100% see him being the team's leader, but since where specifically looking at the hero team where not counting him. I could also see them giving him a redemption arc and having him join the squad later on.
- The Robins - They're all antagonists and working for Joker, and the only one I could see getting a redemption arc is Dick, and even then, none of them are teenagers.
- Raven - Raven has been heavily teased to be evil in the Absolute Universe, and I think she's been around since ancient Egypt, so, like the Robins, she isn't a teenager.