Well, a cool plot in Sailor Moon fanfiction might be exploring the backstories of the minor characters more in - depth. For example, delving into the life of a Sailor Scout before she got her powers. Or perhaps a plot where the Sailor Scouts have to deal with a virus that affects their powers and they have to find a cure without their usual abilities.
One interesting plot idea could be a time - travel scenario where Sailor Moon goes back in time to prevent a major event that led to the rise of a powerful enemy. Another could be a crossover with another popular anime, like having Sailor Moon meet Naruto and they team up to fight a new threat.
An interesting plot could be that Goku and Sailor Moon meet during a multiverse tournament where representatives from different anime universes are competing. They initially don't get along because of their different fighting styles and beliefs, but as the tournament progresses, they realize they can learn from each other. Together, they face off against a cheating opponent who is using unfair tactics to win. Through their combined efforts, they not only defeat the opponent but also learn to respect each other's worlds and ways of fighting.
Well, in Sailor Moon dark fanfiction, a cool plot could be the Sailor Guardians facing an enemy that can manipulate their worst fears. This would make them question their own abilities and loyalties. Also, a story where the power source of the Sailor Guardians is somehow tainted, turning their powers dark and making them struggle to control it. Or perhaps a plot where a new dark Sailor Guardian emerges, with powers equal to or greater than Sailor Moon's, causing chaos in the magical world.
One idea could be that the characters from RWBY end up in the Sailor Moon universe and have to learn the ways of the Sailor Scouts. For example, Ruby could be intrigued by Sailor Moon's transformation and try to adapt her Crescent Rose to work in that magical world.
One idea could be a story where a new Sailor Guardian emerges from a different dimension and has a unique power that can either help or hinder the fight against the Black Moon Clan. For example, she might be able to manipulate time in a different way than Sailor Pluto. Another plot could involve a member of the Black Moon Clan who has a change of heart and decides to secretly assist the Sailor Guardians. This would create a lot of internal conflict within the clan.
One interesting plot idea could be that Natsu, being a powerful fire mage, somehow gets transported to the Sailor Moon universe. He could team up with Sailor Mars, since they both have an affinity with fire. They might face a new enemy that is immune to normal attacks but is vulnerable to the combination of Natsu's dragon - slaying magic and Sailor Mars' spiritual powers.
Well, a cool plot might be that the Dragon Balls are stolen by an evil force from the Sailor Moon universe. So, the Z Fighters have to travel to that universe to retrieve them. Along the way, they meet the Sailor Scouts and realize they need to work together. The Sailor Scouts could also learn about the power of the Dragon Balls and how they can be used for good. They might even help the Z Fighters in their search by using their unique powers to track down the stolen balls.
One idea could be that Ranma somehow gets involved in the fight against the Dark Kingdom in the Sailor Moon universe. Maybe his curse could be related to the magic there. For example, his female form could be mistaken for a new Sailor Scout by the bad guys.
A possible plot is that a powerful dark entity is causing chaos in both the Sailor Moon and Twilight worlds simultaneously. The Sailor Scouts and the Twilight vampires and werewolves have to form an uneasy alliance. Sailor Mercury could use her intelligence to analyze the new enemy's weaknesses. Jacob might teach the Scouts some of his wolf - pack fighting tactics. The story could explore how the two very different groups overcome their differences and work together to save both of their worlds.
Another plot could involve the self - insert becoming a sort of mentor to the younger Sailor Scouts. Maybe they have knowledge from their own world about magic and combat that they can pass on. They could help Sailor Moon, in particular, gain more confidence in her leadership role. This would create a new dynamic within the group and lead to different story arcs as they face challenges together.
One idea could be that the Soul Reapers in Bleach are somehow affected by the magic in the Sailor Moon universe. For example, their zanpakuto (swords) start to gain new powers related to Sailor Moon's elemental powers like fire or water. Another plot could involve a character from Sailor Moon, say Sailor Mercury, using her intelligence to help the Bleach characters understand a new and dangerous threat that has elements of both universes. Maybe she could analyze some strange energy that is a combination of Hollows and the Dark Kingdom's power.