Maybe Sidious is trying to say that it's not just a simple fictional story. It could imply that the events related to him are real in the Star Wars universe in a sense. Like his rise to power, his manipulations, are all very real threats and not something to be dismissed as a made - up tale.
He could inherit the power of Force lightning. Darth Sidious was known for his powerful Force lightning attacks. In the Naruto universe, this could translate to some sort of unique chakra - based lightning attack that is far more powerful than the normal lightning - style jutsu. Also, Naruto might inherit some telekinetic abilities, being able to move objects with his mind or chakra, similar to how Sidious could use the Force for telekinesis.
Well, in theory, it could. Fanfics often like to blend different fictional universes. However, in the official Harry Potter lore, there are no lightsabers. But in a fanfic, an author could come up with some creative magic or a cross - universe event that brings lightsabers into the wizarding world. Maybe a powerful wizard discovers a way to create a weapon similar to a lightsaber using magic and some rare materials.
Well, a great fanfiction idea could be that Darth Sidious discovers the existence of the wizarding world through some dark magic connection. He decides to conquer it, thinking it would be easy prey. But he underestimates the power of the Hogwarts students and their loyalty to each other. Harry Potter would be at the forefront of the resistance, using his skills and the support of his friends like Hermione and Ron.
One idea could be a crossover where Darth Sidious discovers the world of Naruto and tries to manipulate the ninja politics for his own gain. He might see the chakra system as a new source of power to exploit.
Well, it's possible. If we consider the fact that the ancient Sith were the originators of many Dark Side techniques. They might have had a purer, more raw form of the Dark Side power. Sidious, while extremely powerful, was a product of a more refined and political Sith system. The ancient Sith's unpredictable and wild use of the Dark Side could give them an edge in a fictional battle.
Well, if Naruto were the grandson of Darth Sidious in this fanfiction, it would likely bring a dark and different dynamic to the Naruto universe. Naruto's typically positive and bright nature might be conflicted with the Sith influence from Darth Sidious. His values of friendship and hard work could be challenged as the Sith ways are more about power and domination. It could also change the power balance in the Hidden Leaf Village as Naruto might have access to different, perhaps more sinister powers, which would make his fellow ninjas view him differently.
He could find it during one of his missions. Maybe he's exploring an ancient ruin and stumbles upon the lightsaber. It could be in a chest or just lying there, and Naruto, being curious, picks it up.
Pikachu would probably be very curious. It might zap the lightsaber a bit to see what would happen, and then be in awe of the bright blade. It could also get a bit protective of Ash when he wields the lightsaber, as if it senses the added danger.