I think what's sad is that Avatar left us some great ideas for stories, but it was never really treated as important.
Like the Fire Nation colonies. I know the comic had them all living in unity with the Earth Kingdom people, but we know that's not what people are like, and it also takes away a genuinely complex issue and resolves it by saying "there's no issue at all :D".
And this is an issue with no quick resolution, so what happens to these Fire Nation colonies in the time of Korra? Would they see themselves as Fire Nation, or something totally new, and how would they react to Kuvira's mission?
What if the last stand against Kuvira was mounted by Colonials fired by the will to conquest themselves?