In a different path for P5 fanfiction, we could explore an alternate setting. Maybe the Phantom Thieves operate in a different city, like a more rural area instead of Tokyo. This would bring new challenges such as less anonymity and different social structures to deal with. They might have to adapt their methods and personas to fit the new environment.
One possible 'different path' could be changing the confidant relationships. For example, instead of the protagonist building a typical friendship with Ryuji, they could start off as rivals and gradually come to respect each other. This would change the whole dynamic of the story and how the group interacts.