Thinking about it, it might be Wally West. Currently there are no black men on the show, and every other CW superhero show has at least one black man as a main character. Arrow has Diggle and Curtis,
Flash has Joe West and until recently Wally West, Supergirl has James and J'onn J'onzz, Black Lightning has Jefferson Pierce. And Walley is about the only black man that has already been on one of the
other shows. Plus a speedster would be a great asset to the team.