The story would be great... if it made the slightest bit of sense!
Woman forced to leave her true love and marry somone against her will. As cliché as you can possibly get. I much prefer the fan fiction where she and Ozai were originally in love or at least not unhappy together but drifted apart as his ambition drove him to the Dark Side.
Zuko finding out Ozai isn't really his father. There's time for this to turn out NOT to be the biggest cop-out in fiction history, but either way, it's also as cliché as you can get. A fan fic writer could never get away with seriously using this.
But in spite of that, Forgetful Valley, the spirits, the battles with the spirits and the old Water Tribe siblings, Noren and "Noriko" (oh, please!) and Kiyi, and the interaction between Ozai and Ursa in the past would make a great, exciting, suspenseful story... if the set-up made ANY SENSE!
Toph, half the fan base's favorite character, is nowhere to be seen. Iroh, who wanted Zuko to lead the Fire Nation through its transition, tells him to abandon it during a very crucial time. Zuko, the Fire Lord, takes no soldiers, no guards, no back-up to help keep his crazy sister from killing him and his best friends. Said friends treat Azula way too well for someone who has repeatedly tried to kill them and their loved ones (and even kind of succeeded once!). Remember how hard it was for Zuko to get them to accept him in the show? Where's that realism?
Speaking of the show, remember how for 2 seasons, Zuko wanted the throne so badly, he betrayed his beloved uncle for a chance to return home? How he hated the life of a peasant he tried to embrace in "The Guru" but just couldn't? Apparently, all Iroh had to do to get him to let go of his ambition was tell him "You're not Ozai's son," and that would have changed his ambitions and expectations of himself instantly and entirely! He might not be the rightful heir to the throne? That's great! His evil father or sister might end up the rightful heir? No big deal! Tell him Ozai isn't his father, and Zuko, the exiled prince who wanted his honor so badly, just wants to be normal
! Poor Iroh — if only you knew it was that easy!
I'm with you, Aang — this whole plan (Part 1) and Zuko's out-of-character attitude (Part 2) are both ridiculous. Well, at least we already know how it will end thanks to The Legend Of Korra