Yeah, this is something I'm not sure about either. I've never gotten the bar to more than 50% before the conversation with Sayra about Revaire's future, and even that I've only managed on my playthroughs where Katiya's legacy is my announced goal, so it seems like I definitely need that bump. I don't know anything for sure, but maybe befriending Clarmont and having high approval with the servants helps? I know you don't have to invite Sayra to an event to get the peace outcome, because I haven't done that before. It might help, though?