Well, we might see characters from other villages as well. For instance, Gaara. He could be interested in Naruto's silver control because it might offer a new way to protect his village. And there could be a mysterious antagonist who wants to steal Naruto's silver control for his own evil purposes.
Sasuke could be in it. He might be initially skeptical of Naruto's new power but then see its potential in combat.
The Hokage, of course. Depending on which era the fanfiction is set in, it could be Tsunade, Kakashi, or even Naruto himself in some time - jump scenarios. They play a crucial role as Naruto's superior who he serves.
One possible plotline could be Naruto using his newfound control over silver to create unique jutsu. Maybe he can shape silver into weapons or shields in the heat of battle, giving him an edge against his foes.
There could be Sasuke. Since Sasuke is Naruto's rival and often involved in the same major story arcs, he might play an important role in this fanfiction. His sharingan abilities could interact with Naruto's newfound speed in some interesting ways, either as an ally or an obstacle depending on the plot.
Obviously Naruto would be the main character as he has the power to control vacuums. His friends like Sasuke and Sakura could also be involved. Sasuke might be skeptical at first about this strange new ability of Naruto's. Sakura could be trying to find a scientific explanation for it, thinking it has something to do with Naruto's unique chakra nature.
Sasuke would most likely be involved. Since he has a strong bond with Naruto, he would sense something is wrong and try to free Naruto from Kaguya's control. Sakura might also be part of it as she cares about Naruto and would be determined to save him. Kakashi could play a role too, using his wisdom and experience to figure out a way to break Kaguya's hold on Naruto.
The Daimyo of Wave himself would be a main character for sure. Also, his guards or advisors who have a say in the running of Wave. Maybe a young heir to the Daimyo who is being groomed to take over and has his own ideas about the future of Wave.
Sakura could be another main character. She might be shocked by Naruto's arrest and start her own investigation. Maybe she teams up with Sasuke, who also has his own complex feelings towards Naruto. Their combined efforts could play an important role in uncovering the truth.
Sasuke could be a main character. He might be initially interested in the dragon egg for its power but then his relationship with Naruto over the egg could change. Maybe they start as rivals again, but then realize they need to work together to protect the egg.
Perhaps there could be a storm - wizard or a shaman who adopts Naruto. This character would have deep knowledge of storm - related powers and would be the one to guide Naruto in his new journey.