I'm also gunning for Regula to go full Seraph mode on us.
I think it will happen, even tho the storyline is eerily similar to Nael's story.
The General Leo theory I hadn't heard and I would love that as well, but still a Dancing Mad fight would be the best possible ending.

The Emperor is brand new so I don't think he will die, and the game certainly isn't ready for him to be a boss yet.