Stiles is the central figure in this fanfiction. Since he's a born vampire, he has his own set of characteristics and story arcs. His father could also be a significant character. In many fanfictions, the relationship between Stiles and his father is explored, especially when his father starts to suspect that something is different about his son. Additionally, if there are any vampire mentors or antagonists in the story, they would be main characters as well. They would either guide Stiles in his vampire journey or try to stop him from achieving his goals.
One possible interesting plot line could be Stiles struggling to hide his true vampire nature from his friends. For example, he might have to constantly come up with excuses for his super strength or aversion to sunlight. Another could be his discovery of an ancient vampire prophecy that he is a part of, leading him on a journey to fulfill it or avoid it. Maybe he also has to deal with vampire hunters who are specifically targeting him because of his unique 'born vampire' status.
One idea could be that Stiles is turned into a vampire against his will. Maybe he's attacked one night while out investigating something supernatural. As a vampire, he has to struggle with his new urges, like the thirst for blood, while still trying to be the same person his friends know. He might start to see the world in a different light, both literally and metaphorically, as his vampire senses heighten.
The themes usually include the conflict between the human and vampire sides of Stiles. He may still have his human emotions and values, but the vampire instincts can be a challenge. Love and loyalty are also big themes. His friends may or may not accept him as a vampire, and he has to decide how far he'll go to protect them. And there's often a theme of mystery. The vampire world has its own secrets and rules that Stiles has to figure out.
One common theme is the struggle with identity. Stiles has to come to terms with being a vampire instead of human. Another theme is the relationship with his friends. His friends might react differently to his new state, and that's often explored. Also, the control of vampire powers, like the thirst for blood, is a common theme.
His relationship with his friends would likely become more strained. They might be afraid of him or he might be afraid of hurting them. For example, his best friend Scott, who is also involved in the supernatural world, might be worried about Stiles losing his humanity.
Some of his friends might be really surprised. Scott, for example, might be a bit worried that Stiles' vampire obsession could lead him into dangerous situations. Lydia, on the other hand, could be more intrigued and might want to know more about the fanfiction. She might see it as an interesting intellectual pursuit.
One common theme is friendship. Stiles often forms deep and unexpected friendships with vampire characters. Another theme is the struggle between good and evil, as Stiles tries to navigate the complex moral landscape of the vampire world. Also, self - discovery is a big part. Stiles usually discovers new aspects of himself while interacting with vampires.
One great Stiles x Vampire OC fanfiction is 'Midnight Shadows'. It has a really interesting plot where the Vampire OC has unique powers and her relationship with Stiles is filled with mystery and a bit of danger. Another one to check out is 'Blood Ties'. It delves deep into the vampire lore while also exploring the budding romance between Stiles and the OC. There's also 'Eternal Bond' which focuses on how their relationship overcomes various obstacles, both supernatural and personal.
Well, Stiles becoming a vampire in fanfiction could lead to some interesting plot developments. He could use his enhanced senses to solve mysteries more effectively. His nocturnal nature as a vampire might make him seem more mysterious to his friends. He would have to find a way to get blood without harming innocent people. Maybe he teams up with a friendly vampire who teaches him how to hunt animals instead. His life would be completely different, and he'd have to adapt quickly to survive in the vampire world.