I'm gonna drop this fic idea in everybody's lap where Zuko splits in two. Like, after the Agni Kai with his dad, he becomes so conflicted that his spirit rips itself apart. The two halves, Yin Zuko and Yang Zuko, see each other as wholly separate individuals, but the reality is that they're still one and the same—they're both Zuko. This is what he has to realize and accept to be "whole" again, though in the end, he doesn't feel it necessary to return to a single form.
To be more specific, it's a different representation or manifestation of Zuko reconciling with the one half of his identity that comes from Sozin and the other from Avatar Roku. Yin Zuko clings to his pride and the propaganda his family and country have taught him, and he considers Yang Zuko, who recognizes and denounces the personal and global damage caused by those same two things, a traitor. Yang Zuko, in turn, sees his other half as stupid and a coward. Through some sort of spiritual journey that Uncle Iroh may or may not be a part of, he realizes that affection for his country and its culture doesn't have to be mutually exclusive from acknowledging its transgressions against people it's thus far other-ed and wanting it to be better. Y'get my drift?
I think there could be meaning found in Zuko's spirit splitting on its own without any super-natural cause, but I also think Tui and La having a hand in it could be meaningful, too. Like, they don't have any malicious intentions, but the war within Zuko is so great that it draws their gazes as spirits representing duality, yin and yang; thus, to quell the internal conflict, they force him to literally reconcile with himself.
TL;DR A Zuko Joins the Gaang Early AU in which there are two Zukos but they're actually just Zuko who still uses "I" to refer to himself no matter which half is talking, and this greatly confuses Sokka.
