Well, the plot implications are many. Firstly, Naruto's new power might attract new villains who are interested in the Rinnegan. This could lead to new and more dangerous threats. Secondly, it could change his role in the village. He might be seen more as a god - like figure, which could create some jealousy or resentment among some of the villagers. And within the ninja world, the other Kage might have to reevaluate their stance towards Naruto and his village. It could also lead to Naruto exploring new places or dimensions that are related to the powers of the Rinnegan.
Well, it would significantly boost his power. The Rinnegan is an extremely powerful dojutsu. Naruto already has his vast chakra reserves and Sage Mode. With the Rinnegan, he could gain new abilities like the Six Paths techniques. He might be able to manipulate gravity, use the Outer Path to revive the dead (though this has its own moral and plot implications in the fanfiction world). His combat capabilities would be off the charts, making him one of the most formidable characters in the fanfiction universe.
Perhaps Kurama has some hidden ability that allows it to manipulate matter at a fundamental level. Using this ability, it could assemble atoms and molecules to construct a new body for Naruto. This process might be tied to the Kekkei Genkai in the fanfic, where the unique genetic trait plays a role in how the body is formed and stabilized.
One plot implication could be that Naruto becomes a target for more powerful enemies. Since the Rinnegan is such a powerful and coveted dojutsu, many villains might want to either steal it from him or kill him to prevent him from using it. Another aspect could be that Naruto has to learn to control the Rinnegan's powers, which could lead to some internal struggles as he tries to balance his existing powers with this new and extremely potent ability.
One plot implication could be a shift in the power balance in the Naruto universe. With Naruto having the Rinnegan, the Akatsuki or other villainous groups might see him as an even greater threat and target him more aggressively. Another aspect could be the relationship between Naruto and Sasuke. Sasuke giving away such a powerful ability shows a great deal of trust and sacrifice. It could lead to a deeper bond between them, and they might team up more often to face new challenges.
One consequence could be that Naruto becomes too overconfident. With all this new knowledge, he might think he can handle any situation easily and take unnecessary risks. Another consequence could be that his relationships with his friends change. He might seem more distant as he delves deeper into the knowledge, spending more time on his own to understand it all. Also, there could be a power imbalance in the ninja world. If Naruto becomes too powerful too quickly, it could disrupt the existing power dynamics among the villages.
One possible plot could be that Kurama, seeing Naruto in her female form, decides to give her a fox tail as a symbol of their unique bond. This could lead to Naruto having new powers or a deeper connection to the Nine - Tails' chakra. Maybe she can use the tail for balance in battle or even for some kind of new jutsu that involves the tail's movement.
Well, one possibility is that Naruto gains new powers with the Rinnegan. He might use it to finally bring true peace to the ninja world. Maybe he could combine the power of the Rinnegan with his existing Sage Mode and Nine - Tails chakra, becoming an even more formidable force against any threats.
Perhaps in the fanfic, Pein gives Naruto the Rinnegan to create a balance of power. With the Rinnegan, Naruto might face new enemies who are after this powerful dojutsu. He would then have to use his newfound power, along with his existing skills like Sage Mode and Rasengan, to protect his friends and the village. The story could also explore how Naruto's view of the world changes with this new power.
The origin of the bloodline might be from a dimension that Kurama has access to. There could be a race in that dimension with unique abilities, and Kurama was able to extract and transfer their bloodline essence to Naruto. Another possibility is that the bloodline was a gift from the Sage of Six Paths himself, which Kurama was tasked with giving to Naruto at the right time to help him in his fight against the ultimate evil. This would tie in with the overarching lore of the Naruto universe.