An anthology series where each episode, or portion of an episode, is just a small personal story set in the a avatar universe should be take nice and fun. Think "The Tales of Ba Sing Se", but about ground level events of citizens of different nations and times, focusing on a new, usually unrelated character in each episode. It would be a great way to world build without needing an avatar to be around all the time. It wouldn't have to be exclusively about non-benders, but should always be about people doing good.

Just simple stuff like: A sheep-monkey herder in the outskirts of the Earth kingdom defending her flock from hunting rat-wolves. Then she rescues a newborn sheep-monkey that gets washed away in a river during the attack. It ends with her sitting vigilant on a grassy hill, the newborn asleep on her lap, it's mother napping at her side, and surrounded by the rest of her flock also sleeping, secure under her watchful eye.