Another popular Pokemon to include could be Charizard. It's big, strong, and has a cool design. From Avatar, Katara could be included. Her waterbending skills and strong personality would make for great interactions with Pokemon. Maybe she could use her waterbending to heal injured Pokemon.
One idea could be a crossover where Pokemon trainers visit the Avatar world. They could learn bending techniques and use their Pokemon in unique ways to help the Avatar in a great battle. For example, a Pikachu could use its electricity to enhance a waterbender's attack.
Yes, in some fanfiction, Harry could be reimagined as the Avatar. Fanfiction often takes characters from different universes and combines them in unique ways.
A good plot idea could be about an Avatar who loses their bending abilities. They then have to go on a journey to regain them, facing various challenges along the way. Maybe they have to seek the help of a reclusive and powerful spirit who demands difficult tasks in return. Another idea is a story set during a time of peace in the Avatar world, but a new threat emerges from an unexpected source, like a group of non - benders who have found a way to harness dark energy. Or you could do a plot where the Avatar has to deal with a civil war within one of the bending nations, trying to bring balance and peace back.
Yes, it's legal. Fanfiction writers create stories based on the Avatar universe as a form of homage and expansion of the world they love. Most of the time, the copyright holders of Avatar tolerate fanfiction as it helps to keep the fan community engaged and excited about the franchise. However, if someone were to take the fanfiction and try to sell it as an official Avatar product or something similar, that would be illegal.
Well, Naruto's ninja skills would be quite a novelty in the Avatar world. His shadow clone jutsu could be used in various ways, like for scouting or confusing enemies. Maybe he'd learn some bending techniques too and combine them with his ninja moves for some epic battles.
It can add more depth to the characters. By exploring different scenarios in fanfiction, we get to see different sides of Jake and Neytiri. For example, their relationship in non - movie situations.
Jon Snow would be an interesting character to be an avatar. Given his complex backstory and his role in the fight against the White Walkers, as an avatar he could gain even more powerful abilities. Maybe he could have the power to control the elements, which would be a huge advantage in battles. He could use this to create blizzards against the White Walkers or to put out fires during the sack of King's Landing.
One idea could be a story where the two teams compete in a friendly but intense tournament. They might face challenges that test their bending skills in new ways.
Harry Potter himself could be a potential Avatar of Death. Given his connection to Voldemort and all the death and sacrifice he has witnessed, he might develop some sort of connection to death in a more profound way. It would be a very dark and different take on his character, but it could also add a whole new layer of depth.