The Ray
While we’re on the subject of animated webseries, the other one that The CW have in the works is The Ray. After Vixen and Constantine’s appearances in Arrow season 4, The Ray will be the only animated hero not to have any connection to the live-action universe. That has to change, then, and a perfect place for him to pop up would be LoT season 3.
Ray Terrill is a hero with light-based powers and a member of the Freedom Fighters, a superhero team full of lesser-known DC heroes like Black Condor, Phantom Lady and Miss America. Their origins have changed over the years, but the FF tend to come from a dystopian version of the timeline. Seeing as the Legends seemed to find themselves in such a place at the end of season 2, it could be very easy to introduce The Ray and his friends into the show next season.
Incidentally, the character will be the first gay superhero to lead his own show (not including the bisexual Sara Lance, of course). If he stuck around in a main role, then, he could help diversify the cast, which currently doesn’t include a male gay character.