One great fanfiction idea could be the Dragonborn Vampire Lord's struggle to maintain his humanity while dealing with the thirst for blood. He might have to make tough choices between using his vampiric powers for good or succumbing to the dark desires that come with being a Vampire Lord.
A plot could center around the Dragonborn Vampire Lord's search for a cure. He might hear rumors of a powerful artifact or a wise mage who can reverse his vampirism. Along the way, he meets other vampires who either try to persuade him to embrace his new life or are jealous of his power. He also has to deal with the normal threats in Skyrim like dragons and bandits while trying to keep his vampiric nature a secret from those who would hunt him.
The length of Skyrim's story can vary depending on how you play. If you focus mainly on the main questline, it might take around 20-30 hours. But if you explore all the side quests and take your time, it could easily be over 100 hours.
Skyrim's story length really depends on your playstyle. Some players rush through the main story and finish in a relatively short time. However, if you take your time, do side quests, and explore the world, it can last for many, many hours. There's no set time as it's highly customizable.
His Sharingan - if he had it in this godlike state - would allow him to see through illusions in Skyrim. Many of the mages in Skyrim use illusions to deceive their opponents. Naruto could easily counter that. Also, his chakra control could be used to enhance his weapon handling in Skyrim. He could infuse his chakra into a sword or an axe, making it more powerful and able to cut through tougher enemies.