So DC wants to base a show on the New Teen Titans, but already screwed up Wally West and Starfire in the Nu52?
Shows are not tied in too closely so I wouldn't worry about it.
I doubt they would have Kid Flash because of the Flash series, and Red Arrow because of Arrow. Arrow has also taken their bad guys Deathstroke and Brother Blood.
I would guarantee Raven and Wonder Girl. Cyborg would be high on the list. But Beast Boy and Starfire would be pretty expensive in the special effects department. Beast Boy is good Comedic relief though. Jerico would be easy.
Edit. I would love Blue Beetle in there too.
If Arsenal and Kid Flash are out of the running, because of the other shows going on with them, perhaps some other Titans, like Aqualad/Tempest (or Kalduran?) or Jericho or Bumblebee might have a shot. Jericho promises the cheapest power FX, since he just has glowy eyes and then another actor plays being possessed by him. Bumblebee's size changing can be used sparingly (rarely showing her shrunk in the same scene as other characters, to save money, using perspective tricks like Peter Jackson used to disguise the fact that the tallest actor in the Fellowship was the dude playing the Dwarf Gimli). Garth/Aqualad, pre-Tempest, barely had any special effects requirements at all. He was just a super-strong good swimmer, which is only relevant when the writers choose to put the adventure in the water. Don't include that often, and he's just a strong guy. Kaldur'ahn or Tempest would naturally require more effects for their water manipulation or energy powers.
Golden Eagle's right out, if only because every attempt I've seen at man-sized feathered wings, CGI or costume effects, has sucked monkey balls. Even the CGI wings in The Hobbit on the giant eagles were sketchy, and Peter Jackson had dump-trucks worth of money to spend on them.
Duela Dent? Ooh.
Classic Donna Troy/Wonder Girl, strong, fast, both cheap to reproduce. Flight, more expensive. Making a decent looking golden rope could be an issue. Same basic issue for Cassie.
Classic Raven can be done with dry ice (for the clouds that accompany her teleporting) or whatever, and healing is cheap (show 'wound makeup' vanishing step by step), as is her empathy (hand to forehead, 'I sense something!'). Versions able to fly and / or manipulate dark energy or project her soul-self will require a bit more work.
It's also possible that Roy and Wally perhaps being unavailable (and perhaps not, the TNT series might offer up different versions of characters seen on Gotham or the movies or whatever), doesn't mean that another speedster, like Bart, or another archer, like Artemis or Mia or Cissie, won't be available.
I don’t think those Red Arrow/Speedy and Kid flash because the other networks have the license to use those characters.
If they are smart they start small and add in/guest star new characters.
Now for villians I’d say HIVE, Brotherhood, Trigon.
HIVE is sort of being used on Arrow (they've been mentioned as being behind the death of Diggle's brother, though they haven't actually shown up).
Just found out that Cyborg is going to be in the eventual JL movie so not sure if he would be able to be in the Titans TV show. Licensing can be a real @#$% for creativity. But on the other hand limits can sometimes make for better creativity.