Annabeth Chase would most likely be one of his allies. She has always been by Percy's side, and she shares his sense of justice. If Percy decides to take on the gods, she would be there to support him with her intelligence and strategic thinking.
His mother, Sally Jackson, could play an important role as an ally. She has a strong will and has always been there for Percy. Also, Tyson, his cyclops half - brother, could be a powerful ally with his strength and loyalty. And don't forget about the Nymphs. Some of the water nymphs might help Percy since he has a connection to water.
Athena might also be a good candidate. Although she and Poseidon have their differences, she could see Percy's potential and befriend him. She could offer him wisdom and strategic advice for his various adventures.
Maybe Percy unknowingly breaks some ancient and very strict laws of the Gods. For example, he might interfere with some sacred rituals or places that are off - limits to mortals, even demigods like him. In the fanfiction world, the Gods could be very unforgiving when it comes to such violations and decide to kill him as a result.
Zeus is also often paired with Percy. Their relationship is always complex and full of tension in the original stories, so fanfiction can explore this further. Maybe Zeus asks Percy to do a special task for him in order to earn the gods' full acceptance of Percy.
Percy Jackson is likely still one of the main characters. After all, he's the central figure in the original series. And Annabeth might also be there, as she's always been by Percy's side.
Yes, it is quite popular. Some fans like to explore alternate storylines where Percy takes extreme actions like this. It adds a new level of drama and reimagines the power dynamics in the Percy Jackson universe.
I think it would be Magnus Chase. Since Magnus has experience with the Norse world and Percy is used to dealing with the demigod stuff, they could combine their knowledge and skills. Also, they both have a sense of justice and would likely work well together.
Athena is also a favorite. Her wisdom and strategic mind can make for some really interesting plotlines. A fanfic could focus on a demigod who is seeking her guidance or on a conflict between Athena and another god where the demigods get caught in the middle. And her owl is a recognizable symbol that can add a nice touch to the story.
Grover might be the most likely to resist. He has always been very connected to the mortal and natural world. His role as a satyr has been to protect and guide demigods in the mortal world. Becoming a god would mean leaving behind his familiar role and the simple joys of the natural world he loves so much. He might fear losing his identity and his close connection to the forests, meadows, and the young demigods he has befriended over the years.