Timber Wolf also known as Brin Londo a member of the legion of super-heroes he posseses powers such as super strength speed and agility he was experimented on by his father giving him werewolf like abilities but there is a drawback he is prone to beast savagery. This would be good as a Halloween or October episode and possibly show some relation with white canary and her blood lust.
He's quite an obscure character but he has great screen potential.Londo is a bit of a loner so it would be good to see him make a transition to being a teammate. He can also be a bit impulsive with combination to his more beastly side. His tracking skills and heightened senses would be a valuable asset to the team.
Lightning Lad the leader of the legion of superheroes as the monicer suggests he controls elecricity. His real name is garth ranzz. He's a founding member of the legion.
He's got a nice laid back personality which you don't see too much on legends but he can be a bit of a hot head at times. Later he sports a cool lightning scar but no he is not harry potter. For a while Garth has to make do with a robotic arm later being restored by Dr.Zan Orbel. Plenty of cool characters have a mechanical arm such as luke and anakin skywalker and will smith in I Robot.
Batman/Terry Mcginis he needs maybe a slight introduction this amazing man to take up the mantle of the bat in NeoGotham's century. He steals the batsuit to avenge his father's murder and bruce decides to take him on as his protege. Mcginis is still in high school during the cartoon series.
You see a older version of Mcginis in Justice League Unlimited Epiolgue. The future batsuit has a few upgrades like neuro muscular amplification increasing your strength by ten times and microphones in his fingertips activated by touch and a variety of batarangs.
Battalion aka Alexander Lyons made his debut in Team Titans he is a leader of the team titans. He is a very obscure character. He trained the team titans to fight. He's quite strong and fast and highly proficient with firearms.
You could go either way casting him as hero or villian. He would make a good drill sergant for any evil army. ya cheesehead. Battalion is no stranger to time travel.
The Brain primarily opposing the doom patrol he is the leader of the brotherhood of evil. as his name imply he has a genius level intellect and would be a major force for the legends to overcome.
With a name like the brain you know he's more brain than brawn. He is a great at seeing end games and is able to manipulate and deceive others to accomplish his end game a very devious master of manipulation. The aesthetics of The Brain will give a nice sci-fi feel to the show.