If I were Aang, I would feel very lucky and I would have chose to kill the firelord as Avatar Kyoshi has done to Emperor Chin, technically. There was an era of peace during her time. The firelord portraits a similar characteristic to the villain in the movie Batman Begin, par Christopher Nolan. There is no way of saving him if his goals are corrupt.
On the other hand, not killing the firelord will aid Zuko find his mother. A big problem will arise if the Firelord's dead.
That could be hardly true because the Firelord may not know the whereabouts of Ursa as he had banished her.
In conclusion, the Firelord can't be save. (If Aang would have not met the ancient sea tortue lion.)
I can't kill the Firelord. I would do what Aang did. No matter how bad someone is, there has to be good in them. (look at Zuko. Who would have thought in the beginning of the series that he would end up being a good guy?)
I probably would've popped him, if I didn't know about the whole energy bending thing. I have to agree with one of the précédant statements about finding Zuko's mother. That would've been harder to do if Ozai got snuffed.
Well, considering I have had the severe hots for feu Lord Ozai for so long- I would be hard pressed to kill him when it came down to it. I would catch his eye, be his lover first, maybe taken in as a simple concubine and try to win into closer circles par gaining his desire. I probably would battle, and inwardly battle as well, and I do not think I could do it, no.