Kyoshi Warriors/Blue Spirit? That gives me another idea.... (this is adding on to the idea I posted 2 posts back) Instead of Aang going to the NAT when the gAang arrives at Kyoshi Island, he stays, and pretty much the same thing happens, but after the prison break out, he is nowhere to be found. Katara finds Aang's staff, and starts to get worried because Aang would never leave his staff behind, which leads her to believe he's been captured. The scene then transitions to a ship, with Zhao on the deck. A soldier comes up to him and says "Commander Zhao, the avatar has been successfully captured, he was just delivered to us. But where are we going to keep him imprisoned?" Zhao says that they are going to take him to the NAT, because it now a base owned by the FN where weapons are developed. They arrive at the NAT, and we see the temple is inhabited by people. The mechanist comes up to Zhao and asks "What are you doing here? We've already gave you all the machines we owe you this month". Zhao tells him that he is not here for contraptions, but he is carrying a war prisoner and needs a place to keep him. Zhao says if he declines, then he will burn down the temple. The mechanist reluctantly shows Zhao an old prison hold room. Meanwhile, Katara, Sokka, and Suki continue on their search to find Aang to no avail.
The scene cuts back to Aang, and he awakes to find himself in chains in a dark room. Zhao walks in, says some stuff to Aang, then leaves. Then the Blue Spirit comes in, and basically the same thing happens as in the show, except Aang hides Zuko(when he is unconscious) on Zhao's ship, so he can safely escape on his own, without harming the temples inhabitants. Zhao then leaves the island, believing the avatar has fled somewhere else. Aang then meets up with the mechanist. Aang ask him if he is an Air Nomad, and the mechanist replies with no, and explains his backstory(but leaves out that he makes weapons for the Fire Nation). Aang then sees people with gliders up ahead, and asks if they are airbenders, and again the mechanist says no, and explains that. Aang says that he is an airbender, and the avatar, and asks if he can borrow on of those gliders so he can get back to his friends. The mechanist gives Aang a glider, and then Aang leaves the temple.
Then the rest is pretty much the same, except for adding Aang's reunion with Katara and Sokka.