C: Why would Sephiroth call the others "traitors to the Planet" then? He kept referring to Jenova as "mother" and "such is the power of Jenova." He sounds and acts like he is deferring to something.
There are two answers to the question: why did Sephiroth say HE was going to become a god, not Jenova:
1. That "Sephiroth" as Jenova in the first place, or
2. This is pure speculation, but it's interesting: Jenova hated the Planet, hated those who kept her encased for 2000 years. Why would she bother to try to rule it? So, she wants it destroyed. She convinced Sephiroth to summon Meteor with a tale of becoming a god, which will destroy the world and all life on it, not giving a damn about Sephiroth.