One possible motive could be the pursuit of power. Orochimaru is known for his vast knowledge of jutsu. Naruto might think that by joining him, he can gain the strength needed to protect his village better or to bring Sasuke back more effectively.
In a fanfic, Naruto could be tricked into joining Orochimaru. Orochimaru is a master of deception. He might manipulate Naruto into thinking that he has no other option to achieve his goals, for example, by making him believe that the village has turned against him or that only Orochimaru can help him unlock some hidden power within himself.
One possible motive could be to change Orochimaru's evil ways. Naruto might think that by changing Orochimaru's gender, he can disrupt Orochimaru's identity and power structure. Since Orochimaru is so used to being male and having a certain way of doing things, being female could throw him off balance.
Another possible motive is that Orochimaru sees Naruto as a potential powerful ally or tool. Naruto has shown great potential and growth throughout the series. Orochimaru could think that by taking Naruto and molding him in his own way, he could have a powerful weapon at his disposal. He might also want to use Naruto to get back at Konoha in some way, since Naruto is one of Konoha's most important assets.
Well, Orochimaru is a very ambitious and somewhat deranged character. His motives for experimenting on Naruto could be multi - faceted. Firstly, he's always been obsessed with the Sharingan and other powerful kekkei genkai. Naruto, with his own powerful chakra source, might be a step in his research to create something that can rival or even surpass the power of the Sharingan. Secondly, Orochimaru is known for his experiments on humans to enhance their combat abilities. Naruto's natural strength and growth potential could be used to develop new combat - enhancing techniques that Orochimaru could then use for his own purposes, like building a more powerful army or just to satisfy his own scientific curiosity.
Well, in such a fanfic, Naruto joining Orochimaru would be a huge shock to the Naruto -verse. Orochimaru has always been an enemy, so for Naruto to side with him would mean a major shift in the power dynamics. Naruto could learn a great deal about the darker side of the ninja world, but he'd also be in constant danger of being used by Orochimaru for his own purposes. It would be a very different Naruto story, full of moral dilemmas and unexpected alliances.
One consequence could be a shift in the power balance among the ninja villages. Since Orochimaru was a powerful and feared figure, his death might cause some chaos as his former allies or subordinates try to either avenge him or claim his resources. For example, some of his secret labs and experiments might be up for grabs, leading to potential conflicts.
One possible motive could be power. In some fanfics, Sasuke might be driven by an insatiable thirst for power and see Naruto as an obstacle. Another could be revenge, perhaps believing Naruto has wronged him in some way in that alternate story. Or it could be a matter of being corrupted by dark forces, which make him turn against Naruto.
One possible plotline could be Naruto being captured by Orochimaru and forced to endure various genetic experiments. Maybe Orochimaru is trying to extract the power of the Nine - Tails from Naruto in a more invasive way. Another could be that Naruto's friends, like Sasuke and Sakura, attempt a daring rescue mission while Naruto is in Orochimaru's clutches and they face off against Orochimaru's minions.
Well, in such a fanfic, a plotline might involve Naruto's friends trying to rescue him. They could discover Orochimaru's lair where Naruto is being experimented on. Meanwhile, Naruto himself could be developing new and unexpected powers as a result of the experiments, which he then has to learn to control. And there could be a race against time for Naruto's friends to reach him before Orochimaru's experiments cause irreversible damage.
Well, perhaps in the fanfic, Orochimaru tortures Naruto as a form of revenge against the Leaf Village. He might use his various snake - related jutsu to cause pain and harm to Naruto. For example, he could make snakes constrict Naruto, slowly squeezing the life out of him while also injecting him with some sort of venom that causes excruciating pain. And all this while, Naruto is trying to find a way to break free and defeat Orochimaru, relying on his inner strength and the memories of his friends and his training.
Another motive could be Naruto's loyalty to his friends and the village. If Obito is a threat to them, Naruto will put himself in danger to safeguard them. He has a strong bond with his comrades and the place he calls home. Jumping in front of Obito could be his way of showing that he will not let anyone harm what he holds dear, even if it means facing a powerful enemy like Obito.