Holy shit, you're an Aang fag if I've ever seen one. First off the point about them being around each other longer is moot because half the time she was like his mother, 25% of the time he was chasing after her (with no reciprocation on Katara's part), the other 25% is the forced romantic scenes that they had which lacked any sort of chemistry. In fact Zuko and Katara had more chemistry in about a minute in the underground caverns in ba sing se than Aang and her had the entire show. That's a problem. If you can't see why i said Katara acts motherly towards Aang by watching the show, there's no argument I can string together to convince you of it.
As for the second point, you're right, the revenge mission wasn't meant to be romantic at all. The writers at this point had already set up Kataang endgame. Which makes it even more confusing when they still had more chemistry than the endgame couple. They weren't trying to play it romantically, but that's still how it came off because the personalities meshed more than aang and Katara.
Alsp you wave the fact that they got married and had kids in my face like that disproves me saying that it shouldn't have happened if they were trying to tell the best story. I'm not mad, I'm just acknowledging that Zuko and Katara, with the proper build up, would have made a much better couple.