Even Boba Fett could be a main character. He's used to dealing with dangerous situations. In a zombie - infested Star Wars world, he could be hired to retrieve something from a zombie - filled area. He'd use his weapons and his bounty hunter skills to survive the hordes of undead while also facing other threats in the galaxy.
An old Clone Wars veteran, either a clone or a non - Jedi military figure, could be the main character. They have seen the destruction of Order 66 and now suspect there is more to the story with Order 67. Their knowledge of the past wars and military strategies would be useful in uncovering the truth.
They could be the children of Luke Skywalker. Maybe he had triplets in secret, and they inherit his strong connection to the Force. Each of them could have different personalities, like one being very brave and impulsive, one being more cautious and intellectual, and the other being empathetic and diplomatic.
The main characters could be a group of bounty hunters. They get hired to investigate the origin of Order 69, thinking it might lead to a big payday. As they dig deeper, they find themselves in the middle of a galactic conspiracy. There could also be a Sith apprentice who is using the chaos caused by the order to rise in power within the Sith hierarchy.
Obviously, the apprentice themselves would be a main character. They could be a young and ambitious force - user, eager to learn from their master. The master, who is likely a powerful Sith or Jedi, depending on the nature of the fanfiction, would also be a key character. And then there could be a rival apprentice or a mentor figure from the apprentice's past that plays a significant role.
A natural choice for a main character could be Spartacus himself. Transplanted into the Star Wars universe, he could be a freedom fighter against the Empire. He could inspire the downtrodden species in the galaxy with his unwavering will for freedom. Another could be Anakin Skywalker. If he were to meet Spartacus, he might learn different perspectives on leadership and freedom. Spartacus could show Anakin that true power comes from the people, not from the Sith Lords.
Homura could be a great main character. She could be a Jedi - like figure, using her time - looping abilities in a way similar to how a Jedi uses the Force. She might be on a quest to save Madoka, who could be a powerful Force - sensitive being in this fanfic.
For main characters in a 'Star Wars Droid Rebellion' fanfiction, there could be a group of droids. Firstly, an old medical droid that has seen too many droids being deactivated without proper care. It decides to use its knowledge of droid anatomy to help the rebels. Then there's a security droid that has been reprogrammed by accident to have emotions. This security droid uses its combat skills to protect the other rebels. And finally, a droid engineer who creates new weapons and defenses for the droid rebellion, using its skills to turn the odds in the droids' favor.
Kylo Ren could also be a main character, even if he's dead in the official story. Fanfiction has the freedom to bring him back in some form, like as a Force ghost or through some time - travel shenanigans. Another possibility is Finn. He has grown so much throughout the movies and could have an important role in the future of the galaxy in this fanfiction.
A young Earthling who is discovered to be extremely Force - sensitive could be a main character. He or she could be mentored by an old Jedi master and go on a journey to learn about the Force and their place in the Star Wars universe.
A vampire lord from the 'Star Wars meets Vampires' world could be a main character. He rules over a group of vampires and is constantly looking for ways to expand his power. When he discovers the power of the Force, he becomes determined to use it for his own dark purposes.