One idea could be a story where Steven, despite being blind, discovers a new power within himself that is related to his sense of touch. For example, he can sense the emotions of the Gems through their gemstones when he touches them. This would add a new dimension to his relationships with the other characters.
Maybe a fanfic where Steven's blindness leads him to rely more on his friends in ways he hadn't before. The Crystal Gems have to adapt to protecting him more closely and in different ways. They could also learn a great deal from Steven's new perspective on the world, which could strengthen their bond as a group.
One idea could be a gem oc who was created with a unique power that the other gems don't understand. For example, the power to communicate with non - sentient objects. This could lead to all sorts of adventures as the oc tries to figure out how to use this power and the other gems try to figure out if it's a threat or a valuable asset.
An interesting Steven Universe OC fanfic could focus on an OC who is a healer Gem. This OC could have the power to heal not only physical wounds but also emotional traumas. In the fanfic, they could travel around the universe, helping Gems and humans alike. They might face challenges like being drained of their energy when they heal too many at once, or they could encounter Gems who don't believe in their powers. Maybe they join Steven and the Crystal Gems on their adventures and use their healing skills to mend relationships within the group.
One idea could be that Lars and Steven go on a space adventure together. They might encounter new gem species and have to work together to solve problems. For example, they could find a planet where the gems are in a civil war, and Lars and Steven use their unique skills to bring peace.
A more emotional plot could be an OC who was once part of the Homeworld gems but defected. They have a lot of guilt and self - doubt because of their past actions. In the fanfiction, they try to make amends by helping the Crystal Gems. But they constantly fear that their old allies will come after them. This internal struggle and their journey of redemption could be a really interesting story.
A third idea would be to create a story where the Black Pearl has a sentient being inside it. This being could communicate with Steven and the others telepathically. It could be a source of great wisdom or power, but also comes with a dark side that the characters have to deal with. For example, it might try to possess one of the characters in order to achieve its own goals.
Perhaps an alien OC from a water - based planet. Their physiology is adapted to living in water, but they have the ability to create water - based constructs. They come to Earth in search of a special type of gemstone that is said to have the power to heal their ailing home planet's oceans. This would create a plot full of adventure as they team up with the Crystal Gems to find the gemstone.
One idea could be that Naruto and his friends end up in the world of Steven Universe. They could team up with the Crystal Gems to fight a new common enemy that has the power - stealing abilities like Orochimaru and the ability to corrupt gems like the Diamonds' powers. Naruto's jutsu could be a new and strange concept for the Gems, and Steven could try to understand Naruto's ninja way.
Well, the OC could be a human - gem hybrid. This would make them an outcast in both human and gem society at first. But as the story progresses, some of the main characters like Pearl, Amethyst, and Peridot start to form a bond with the OC. Maybe they are all intrigued by the OC's dual nature and the way they navigate between the two worlds. This could lead to a harem - like situation where they all have different relationships with the OC, some more platonic, some with a hint of romance.
Perhaps in the 'Steven Universe Watch the Future fanfiction', there could be a plot where Steven travels to a different dimension within the Gem universe. In this dimension, the rules are different, and he has to adapt quickly. He meets alternate versions of his friends who have different personalities or powers. This could lead to a self - discovery journey for Steven as he sees how different choices could have led to different outcomes. He then has to find a way to bring back something from this dimension that can help save his own world from a brewing disaster.
One idea could be Lars exploring a new planet full of strange, sentient plants that communicate through colors. He has to figure out how to interact with them to get the resources he needs for his ship.