Martian Manhunter
Supergirl (David Harewood) or Synder cut (Harry Lennix).
I love this character and love more the idea he is secretly operating these high-level government positions or agencies while being a undercover superhero.
I would say with the rise of popularity in conspiracy theories and internet phenomenon of the SCP foundation, we should have a series revolving around J’onn J’onzz investigating strange or bizarre Si-fi and fantastical elements of the dc universe.
One character I would definitely include is mr. Bones.
Either a antagonist or a morally grey ally who J’onn J’onzz reluctantly works alongside with.