If Viggo really is involved, it has to be Lex. I never wanted him as Zod but liked him for Lex so that would be sweet

Zod in general was not necessary imo. I understand they will use him differently/reinvent. It's just that with Brainiac, Lex, Metallo, Darkseid, even Doomsday in some capacity were all worthy villains that could be used. I just don't think Zod was needed if we are moving away from Donnerland completely. With that said, we have to accept it and I have no doubt it will be done in a way less corny than on previous film/tv series.