I've actually got some pretty significant issues with this. First, Princess Yue would be her older sister and is actually alive in this universe. She's only sixteen. With no mention of having an older sister, I don't want to significantly edit the pretense by allowing a sister three years senior to the present heir to the Northern Water Tribe.

Secondly, people in the Northern Water Tribe aren't really sad or oppressed. As I explained in, they're actually the [b]least[/b] affected by the Phoenix Kingdom in the whole roleplay. They're pissy about it, sure, but they're not going to be moping around. They still have an incredibly strong sense of culture and self-identity.

Thirdly, Chief Arnook wouldn't be pressing any form of alliance with the Southern Water Tribe. I believe I even go as far as saying the Northern Water Tribe considers them 'debauch'; they're not on terms. While the Northern Water Tribe has a distaste and for the Phoenix Kingdom occupation and taxes, the Southern Water Tribe is fairly complacent and is making bank on technological advancements and their new ability to fish at a hugely more productive rate due to coal engines and superior boats. 

There are quite a few conflicts here that I do needs addressed quite sufficiently. Although the roleplay here will be casual, the setting is very strong. Also, keep in mind the strong sense of chauvinism within the Northern Water Tribe. Pakku refused to train Katara until he found out she was his grand daughter because she was a woman. Pakku is dead now, but that sense of chauvinism still exists. If you make her younger, she's not going to miraculously develop Icebending - that's a fairly advanced form of waterbending and it is a taught one. You only see tribal benders use it. As I said before, cultural influences will be a huge aspect in this roleplay and the Northern Water Tribe culture, as per canon, just plain doesn't teach women to waterbend.