If my advie can ever get some unique items, I'm excited to see where this goes. The idea of simply awarding the title of "Emperor for the Year," as it sounds like, is kind of odd though.
My real question is about powers. It sounds like the only powers of the emperor are to declare open or restricted seasons. Anything else? Power to... define common external diplomacy? Legitimize (or de-legitimize?) rulers of participating realms?