One idea could be an OC who is a new kid in town and tries to bridge the gap between the Greasers and the Socs. They might use their unique perspective from a different place to show both groups that they're more alike than they think.
An interesting plot could be an OC who is secretly related to one of the main characters. This revelation could change the dynamics within the group. The OC could struggle with whether to reveal their relation and how it would affect the relationships that are already established in the story.
One idea could be an OC with a unique power, like the ability to manipulate sound waves. They could join the Outsiders and use their power in unexpected ways during battles, for example, creating sonic illusions to confuse enemies. Another plot could involve an OC who is from a different dimension and has to adapt to the Young Justice Outsiders' world while also bringing some of their own world's knowledge and technology. Or perhaps an OC who has a personal vendetta against a villain that the Outsiders are also after, and they initially clash with the team but then learn to work together.
Another plot could be a time - travel story within the 'the outsiders' universe. For example, a character travels back to the events before the big rumble and tries to prevent some of the tragedies from occurring. This would involve a lot of character interaction and changes to the original storyline.
A great plot for Young Justice Outsiders fanfiction could involve a crossover with another DC team or universe. Maybe the Outsiders accidentally end up in an alternate dimension where they have to team up with unlikely allies to get back home. This would introduce new dynamics and challenges for the characters.
One idea could be to explore what would happen if Ponyboy became a successful writer earlier. He could use his writing to change the perception of the Greasers in the town.
One idea could be that the Outsiders are called in to help the Young Justice team when a new, powerful and mysterious villain emerges. This villain has a unique power that neither team has faced before, forcing them to combine their skills and resources.
Another plot could revolve around an OC who is a Spartan trainee that doesn't quite fit the mold. They have a different way of thinking and approaching combat. In Halo 4, they end up being the key to solving a mystery related to the Prometheans. Maybe they find a way to communicate with the Prometheans and convince some of them to stop fighting the humans.
One idea could be an Otsutsuki OC who comes to Earth not for conquest but to study the unique life forms here. They could befriend some of the local ninjas and learn about the concept of friendship, which is alien to the Otsutsuki. This would lead to a series of adventures where they have to protect their new friends from other more hostile Otsutsuki members.
One idea could be an OC who is a long - lost relative of Moana. This OC could have been separated from the family during a great storm years ago. They could have unique skills, like being able to communicate with a different type of sea creature that Moana has never encountered. This would bring new adventures as Moana and the OC try to figure out how this new discovery could help their island.
One idea could be exploring the origin of the OC in the covenant world. Maybe they have a special power that sets them apart from the regular covenant members.
One idea could be an OC who is a new Wolfblood in a pack and has to prove themselves. Maybe they have a unique power that the others don't have and they have to learn how to control it while fitting into the pack's hierarchy.