Gus Fring as Lex Luthor? Yep that would work for me. Esposito has an ability, as shown in his portrayal of Fring on BREAKING BAD, to be an outwardly unassuming and respected businessman who is secretly a very bad, bad man. And that is likely what this version of Lex Luthor will be. he is going to be a respected and beloved citizen of metropolis who is known for his philanthropy but who id really all bout accumulating power at any cost. That dual nature fits into the strengths of Esposito who can pull of friendly and warm just as well as he can pull of chillingly cold and evil.