Another idea is to create a story where the rules of the Grail War are changed. For instance, instead of seven Servants, there are only three, and they have to complete different tasks to win. This would completely change the dynamics of the story and lead to new and exciting interactions between the characters.
One idea could be to have Naruto characters participate in the Holy Grail War. For example, Naruto himself could be a Servant, perhaps with his chakra being a unique form of mana. His skills like the Rasengan could be reimagined as powerful Noble Phantasms. Another idea is to put the Fate Stay Night characters in the Naruto world. They might have to deal with things like ninja clans and the politics of the hidden villages while also trying to find a way back to their own world.
Well, perhaps the Pokeballs in this fanfic could be like the Command Spells in Fate Stay Night. A trainer might use a Pokeball to summon and control a powerful 'Pokemon - Servant' hybrid. And the different regions in the Pokemon world could be the battlefields for the Grail War. The trainers would travel around, catching and training their unique Pokemon - Servants while competing for the Grail.
One interesting idea could be exploring different routes for the characters. For example, what if Shirou had chosen a different Servant at the start? Another could be delving deeper into the backstories of the Servants, like revealing more about their lives before they became heroic spirits. Some fanfictions also play with the concept of alternate universes, where the rules of the Holy Grail War are changed completely.
A plot could be that Mordred is summoned by a powerful ninja as a last - ditch effort to fight against an ancient evil that has emerged in the Naruto world. This evil has powers similar to some of the powerful Servants in Fate Stay Night, so Mordred's expertise is needed.
A cool 'fate stay night crossover fanfiction' idea might be a crossover with 'Final Fantasy'. The different classes and magic systems in Final Fantasy could blend well with the Fate universe. For example, a character from Fate could learn the job classes from Final Fantasy. Also, a crossover with 'Persona' could be interesting. The Velvet Room and the concept of personas could be integrated into the Fate world, adding a new layer of mystery and power to the story.
Another idea is an OC gamer who creates a virtual reality game based on Fate Stay Night. But then something goes wrong, and the game world and the real Fate Stay Night world start to merge. This could lead to all sorts of interesting scenarios, like the OC having to team up with in - game characters to fix the mess while also dealing with the power struggles in the Fate universe.
One idea could be a crossover where characters from Fate Stay Night are transported to the world of Game of Thrones. For example, Saber could be a powerful knight in Westeros, facing off against the likes of Jaime Lannister. Another idea might be that the magic system from Fate Stay Night is introduced into the Game of Thrones universe, causing chaos among the different houses as they vie for control of this new power.
The power - up systems are also quite engaging. It might involve collecting items or completing quests within the fanfic's world to make a character stronger. This adds a new layer of strategy and development to the story. In a 'Fate Stay Night Gamer Fanfic', it could be that the Masters have to find magical artifacts to boost their Servants' powers, and this could lead to all kinds of new adventures and interactions.
One idea could be exploring Archer's internal struggle more deeply. Maybe show his memories of past battles and how they affect his decisions in the Fourth War. Another could be to create a scenario where Archer has to team up with an unexpected character from the Fate universe.
Another interesting plot might be a 'what if' scenario. What if Shirou had to enter Rider's world, like the world she came from before being summoned in Fate Stay Night? He would be completely out of his element, and Rider would have to be his guide. This could lead to many comical and heart - warming moments as Shirou tries to adapt and they grow closer.