In a Six Paths Naruto crossover fanfiction, a great plot could be Naruto being sent to a post - apocalyptic world. He would have to use his powers to help survivors and fight against mutated creatures. The survivors might initially be scared of him, thinking he's some kind of new threat. But as they see him fighting for them, they start to trust him. Naruto could also find a way to bring hope back to this desolate world by using his Six Paths powers to start rebuilding and restoring nature.
One idea could be Naruto from the Six Paths Sage mode getting crossed over into a modern-day world. He could use his powers to fight against new types of villains like super - powered criminals. Another plot could involve a crossover with a different anime universe, like Naruto meeting characters from One Piece and having to team up to stop a common threat that endangers both their worlds. Maybe a powerful ancient evil that has the ability to disrupt the balance of chakra in Naruto's world and the Devil Fruits' power in One Piece's world.
A cool plot could be a crossover where Naruto in his Six Paths form enters a world full of magic, like the Harry Potter universe. He might have to learn how to adapt his chakra - based powers to work with magic. For example, using his Rasengan in combination with a spell. Or perhaps there's a dark wizard who wants to steal Naruto's chakra for his own evil purposes. This would lead to some epic battles between Naruto and the wizarding world's dark forces.