Cont.
Earth Kingdom becomes a bit tricky; since the ancestor screwed the pooch on the Air Nomads, im pretty dam sure that they will not accept any sort of peace. So the better chance is to simply starve them out, or force them to captiulate via besieging their capitols. Sure, they can last incredibly long, but at the same time, but there is no need for me to waste time and money on taking them. Simply build up around them, and work towards breaking down war relations. What I would be willing to accept is to turn Ba-Sing-Se into Hong Kong situation, where they are techincally part if my kingdom, but economically and politcally seperate.
Now, the real pinch is the Avatar himself. This is where shit gets intense, because Aang is still going to be pissed about the whole AIR TEMPLE RAIDS BEST DAY 4 LIFE genocide. Plus, he can fuck my ass if I push for combat. Even worse, he is THE Avatar, he has way more clout when it comes to telling me off, and upsetting my political agenda.
So, how do I beat him? By first, owning up and admitting that Sozin was a fucking monster, and was totally in the wrong. If anybody is pissy about my dishonorable actions, I roast him.
After that, I try to invite the Avatar into the Fire Kingdom directly. Keep Azula and Zuko far, far, FAR away from him. Infact, the only time I would consider even having Azula with a 100,000 mile radius, is in some hairbrained scheme in which I send Azula after Aangs dick, in a attempt to sway him to my side. If she gets pregnenant, even better, since now the Avatars kid is fire nation.
Once Aang is in the fire nation, be sure to show him how great things are. If he thinks the Fire Nation is a example of the whole world, even better, but if not, well, It would be best to show him the better parts of the kingdoms.
It might also be a valid strategy to teach him Fire Bending, and than give him my authority to fix roam the Fire Nation, ensuring the ethical treatment of the occupied provinces.