Oh, these both sound fun! As for the what-if, I'm gonna have to think on it. Torn between two right now though:

One, Castiel never rebells and therefore doesn't join up with the boys to try and stop the apocalypse.

Two, he decides to side with Lucifer during their conversation in Carthage.

EDIT: Or or or Clairestiel. All fear the little blond girl angel.