Well, a possible plot might involve Blue Agate being out of her element in a situation that Steven is very familiar with, like a human party. Steven helps her navigate through it and she starts to see the appeal of human ways. Or perhaps they get caught in a time - loop and have to keep reliving a particular day until they figure out how to break it together.
A more complex plot could be that there is a power struggle among the Gems and Blue Agate is caught in the middle. Steven, with his unique connection to both the Gem and human worlds, tries to mediate. He uses his compassion and understanding to help Blue Agate make the right choices. Along the way, they face challenges from other Gems who don't trust their alliance, but they persevere and end up changing the Gem hierarchy for the better.
In a fanfiction, perhaps there is a conflict involving the three. Steven Universe has his own way of handling things with his pacifist approach. Holly Blue Agate has her Gem way of thinking. And Lemon, as a human, might have a completely different perspective. The story could explore how they resolve their differences.
I'm not sure about specific 'blue agate lemon' fanfictions in Steven Universe. However, you can try searching on popular fanfiction platforms like Archive of Our Own. There you might find various takes on Blue Agate in the Steven Universe universe that could potentially be what you're looking for.
Archive of Our Own (AO3) is a great place to start. It has a vast collection of Steven Universe fanfictions, and you might be able to find ones related to Blue Agate and with the 'lemon' aspect there.
One challenge could be getting their personalities right. Steven is very empathetic and kind - hearted, while Blue Agate has her own Gem - related traits and behaviors. Another is creating a believable relationship between them, as they come from different parts of the Gem world. Also, staying true to the overall lore of Steven Universe can be difficult.
Often, the best way to find a good fanfiction involving these characters is to ask in fan communities dedicated to Steven Universe. They might have read some really engaging stories that involve Holly Blue Agate and Lemon. You could also check reviews on the fanfiction websites to see which ones are highly rated.
One idea could be that Steven tries to understand Blue Diamond's past traumas and helps her heal. Maybe he uses his unique powers of empathy to break through her cold exterior.
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.
One idea could be that Peridot and Amethyst are on a mission together and they start off bickering like they often do in the show. But as the mission progresses, they start to understand each other's strengths better. For example, Peridot's technical knowledge and Amethyst's physical power combine to defeat a new kind of enemy. Another plot could be them exploring a part of the Gem world they've never been to before and having to rely on each other to survive. Maybe they discover an ancient Gem relic that has the power to change the way Gems interact with Earth. This could lead to some really interesting character development as they figure out what to do with this new discovery.
One common plot element is the exploration of Blue Diamond's past through her interaction with Steven. Another could be a situation where they are forced to rely on each other in a difficult situation. For example, they might be stuck in an alien environment together.