In the fanfiction, Ruby and Sapphire could be having trouble adjusting to life in a new town. Steven, who has experience with change, could introduce them to new friends and show them all the fun things about the place. Meanwhile, they could teach Steven more about their unique Gem culture, like how they fuse and their special powers. This would create a story full of cultural exchange and friendship building.
One plot idea could be that Sapphire and Ruby are having a disagreement about how to best protect Steven. Sapphire, with her future vision, sees a potential threat approaching in a very different way than Ruby does. This leads to some tension between them as they try to figure out the best course of action for Steven's safety.
A really interesting plot for a Pokemon Ruby and Sapphire fanfiction could be set in an alternate Hoenn region. In this version, the roles of certain Pokemon types are reversed. For example, Water - type Pokemon are rare and Electric - type Pokemon are the dominant force in water - based areas. The main character could be a trainer who has to adapt to these new rules. They might have to find creative ways to battle and train their Pokemon. This could lead to some really unique and exciting adventures, as they encounter different challenges and make new friends and enemies along the way.
One idea could be exploring an alternate universe where the starters of Ruby and Sapphire have different evolutions. Another could be a story focused on a side character from the manga, like giving a backstory to a Gym Trainer. Maybe also a story where the legendary Pokemon Groudon and Kyogre form an unexpected alliance instead of their usual rivalry.
Perhaps a fanfic could be about a Pokémon from Ruby and Sapphire that gets lost in a different region. The Pokémon has to find its way back home while making new friends and facing challenges in the unfamiliar environment. Along the way, it could encounter different trainers and Pokémon species, and the story could show how it adapts and overcomes obstacles to return to Hoenn.
One idea could be exploring a new mega evolution for a less - known Pokemon in the Hoenn region. For example, making Linoone have a mega evolution with a unique design and new abilities. Another plot could revolve around a trainer who discovers a hidden, ancient Pokemon that was thought to be extinct in the Hoenn caves. This could lead to a race among different trainers and teams to either protect or capture it.
One idea could be focusing on a trainer who is trying to reunite the two legendary Pokemon of Ruby and Sapphire, Groudon and Kyogre, to stop a greater threat that emerges when their power imbalance causes natural disasters. The trainer has to travel across both Hoenn regions, facing challenges from different gym leaders who have different views on how to handle the situation.
Perhaps past versions of the Crystal Gems meet their future selves. They could be shocked by how much they've changed, or they might learn valuable lessons from each other. The past Gems could see how their actions in the past led to the future they now inhabit, which could be a really interesting exploration of cause and effect.
Love is a very common theme. Their relationship is often explored in-depth, from the early days of their meeting to their deep, abiding love as Garnet. Another theme is loyalty. They are always there for each other, and this loyalty is highlighted in many fanfictions. For example, in stories where they face challenges together, their loyalty to each other never wavers.
The unique relationships. Ruby and Sapphire's love for each other and their new role as parents to Baby Steven create a lot of interesting story possibilities. Their different personalities also add depth. Ruby is more fiery and impulsive while Sapphire is calm and collected, and seeing how they interact with Baby Steven, who has his own charm, is fascinating.
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.