To start with, I don't really see the problem of giving him spiritual conflict from his ancestors as spiritually is a big part of the series. And given the existence of the Fire Sages, it seems the Fire Nation have placed spiritually as something important.
Axrendale wrote: |
I quote Iroh: "Good and evil will always be at war inside of you Zuko - it is your nature, your legacy". Zuko will, according to Iroh (whose advice can usually be trusted), always have the internal conflict that prevents lightning creation. He's going to have to stick with plain old firebending. |
While that played a part of the conflict, I believe the main source of the conflict was his lack of direction. His actions of the first two seasons were based on what he thought he wanted. As of Nightmares & Daydreams, he knows what he wants.