As long as this is the epilogue:

Aang dies at the hands of the Fire Lord (Ozai dies too). Zuko takes Katara, but leaves her and lives with his Uncle who at this point is old has gotten sick and is in depends. Katara takes care of a bunch of kids she made with Zuko alone. She grows obese and at this point her image is so disturbing the Katara we knew during the war is a relic and far cry from the past. Katara dies of heartfailure, but her kids can't do anything about it, she dies, paramedics fork lift her carcass out of the house. Zuko starts to question himself again and realizes his inner homosexual love for Sokka. Unfortunately Sokka does not reciprocate, btw he left Suki and walked the path of a casanova. He gets STD's from all the woman he slept with and returns to find Suki has committed suicide via sepukku. Sokka dies at the hospital after the diseases get the worst of him. Zuko still alone finally finds comfort with Haru and they live together somewhat happy. Meanwhile, Mai upset over Zuko leaving her for Katara turns to prostitution, then cuts her wrist to death and she dies with Suki (ritual suicide). Azula who was improsined thought to be too evil to contain yet too hot to kill. So they gave her a lobotomy and Ty Lee moves and takes care of her *spoon feeds Azula* They have lesbian sex and die happy. Oh and Iroh walks away in dipers running away from his home ahamed and looking for something better. He disappears from the rest of the world somewhere....

Fire Nation scientists crack the secret of the atom. The race is on for the Fire Nation to enrich enough uranium to create atom bombs to drop on strategic cites. When the Fire Nation completed there atomic bomb project, the Water Tribes and Earth Kingdom troops have gathered a couple of miles out side the Capital City in a barren plain for the final battle to decide the fate of the world. Aang goes into the Avatar state to get ready for the battle to come. Then the Fire Nation and drops the atom bomb on them killing them all, except Zuko who was captured and ass raped by Azula for the rest of his live. With the main force of there enemy's destroyed the Fire Nation pretty much took over the world. Most people thought that that would be a bad thing. Its turns out that the Fire Nation are a force of good. They build schools, hospitals, houses, temples, farms, and other buildings to help out the community. The Fire Nation also spends up the growth of new teleology. The Fire Nation also clam that the Northern Water Tribe were sexist, the Air Nomads didn't use the land, and the Earth Kingdom were oppresses who induced a feudalistic system on there people and dividing them into classes. Under the Fire Nation the Avatar world experiences peace and prosperity.

The End.

In my scenario, Zuko dies and Aang becomes a wandering, celibate ascetic.

Setting up Azutara.