One idea could be exploring the character's backstory more deeply. For example, how they came to be in the situation they are in the original story. Another could be a crossover with another related fandom, bringing in new elements and characters.
One idea could be the child of the emperor having to navigate the complex politics of the court while hiding their true identity. Another could be the character's journey to discover their heritage and claim their rightful place in the empire. Maybe the child is exiled and has to fight their way back to power.
The plot could involve the child being sought after by various ninja clans who want to use the power of the Kyuubi within the child for their own purposes. The child, with Naruto's teachings, resists and tries to find a way to use the power for the good of the village. Maybe the child discovers a new form of chakra control that combines Naruto's Uzumaki heritage and the Kyuubi's power.
A great plot idea is that the child has a special connection to the sea, like Percy, but also has Annabeth's wisdom. So they use this combination to solve a mystery that has been plaguing Camp Half - Blood for years. For example, the mystery of why some demigods' powers are fading. Another could be that the child gets sent back in time and has to interact with their parents when they were younger. This could create some really interesting situations and challenges for the child.
One idea could be that Harry discovers he has a unique magical ability that even Dumbledore doesn't know about. This ability could be related to his connection with the very essence of magic. For example, he might be able to communicate with magical creatures in a way no one else can, which leads him to uncover secrets about Hogwarts' past.
One idea could be exploring how the child of prophecy discovers their true power earlier than in the original Naruto story. Maybe they start to unlock unique jutsu that no one has ever seen before, which changes the course of the ninja world.
Well, a great plot could involve a power struggle within the world of Highschool DxD related to the Ice Storm Dragon. For instance, different factions might be vying to control the power of the Ice Storm Dragon for their own purposes. The fanfic could focus on how the protagonist gets caught in the middle of this struggle and has to navigate through various challenges, including political intrigue and battles, to either protect the Ice Storm Dragon or prevent its power from being misused.
Perhaps the child OC is on a quest to find a missing family member in the post - apocalyptic world of The Walking Dead. They could encounter various groups along the way, some friendly and some not, which would create a lot of tension and character development.
One idea could be exploring the relationship between the new character, the Demons Child, and the existing Hogwarts students. Maybe the child has unique powers that both intrigue and frighten others.
One idea could be a story where a young wizard from the Harry Potter world accidentally travels to the Bleach universe. He could discover his newfound spiritual powers and try to find a way back home while getting involved in the battles against Hollows. Another plot could be a crossover where the Hogwarts houses are somehow related to the different Soul Reaper squads in Bleach. For example, Gryffindors could have an affinity with the more combat - oriented squads.
A cool plot idea could be that the child has a unique power that neither Robin nor Raven have. This power could attract the attention of an ancient evil force that was once sealed away. So, Robin and Raven have to team up with their friends to not only protect their child but also the whole world from this new threat.