Perhaps a minor character from the original Fate series could be promoted to the main character. For example, a bystander in one of the battles who witnessed something extraordinary and was then drawn into the world of the Holy Grail War in a more central way in the 'a new fate fanfiction'.
It could be an ordinary gamer who has spent countless hours playing Fate - related games. So when they are transported to the Fate universe, they are the main character.
It could be a young hobbit who discovers a hidden power within himself. Hobbits are not typically known for great power, so this would be an interesting twist. He could be fated to use this power to save Middle Earth from a new and unknown evil.
Kagome might be the main character. As she's from the modern world and has a big influence on the events in the feudal era, she could be the one who gets a chance to change the fates of everyone. For example, she could use her modern knowledge to change the course of battles or relationships in the story.
Natsu could be a great main character. His hot - headed nature and powerful fire magic would make for an exciting adventure around the Gate of Fate. He could be drawn to it by the mystery and the potential power it holds, and his journey to understand and protect or use the Gate would be full of action.
I think Spider - Man would make an interesting main character. He's young and has a different perspective compared to the more experienced Avengers. His journey of growing up and becoming a more integral part of the team could be a central theme in the fanfiction. He also has his own set of personal problems like school and his relationships which could add depth to the story.
It could be an ordinary person from our world, like a high school student. They're suddenly thrust into this new world and have to adapt. Their inexperience in this new environment can lead to many humorous and exciting situations.
It could be a new character who has been brought into the Fate Stay Night world with gamer - like abilities. This character might be from our world and has to use their gaming knowledge to survive and thrive in this new and dangerous environment.
It could be an ordinary person who has been pushed to the edge. For example, a young man who lost his family to a powerful and corrupt group and decides to take matters into his own hands.
It could be a young and inexperienced trainer who is just starting their journey in this new world. They have big dreams but a lot to learn.
A young prodigy who has been underestimated all his life. Fed up with being pushed around, he uses his intelligence and unique abilities to rise to power and become the world overlord.