Well, Hermione would be a great addition. She could use her intelligence to help Harry and Moka understand the different aspects of their two worlds. For example, she could research about yokai and find ways to use magic to help Moka control her vampire side better.
Dumbledore would be an interesting character in this fanfiction. His wisdom and powerful magic could be crucial in dealing with any major threats that might come up in the story. He could also offer guidance to Moka about her powers and how they can be used for good in a different context than she is used to.
Definitely Sasuke should be included. He could have some interesting interactions with Inner Moka. Maybe he's initially suspicious of her vampire nature but later comes to respect her skills. Sakura could also be a great addition. She could bond with Inner Moka over their shared strength and determination. Kakashi would be another good choice. His calm and experienced demeanor could contrast well with Inner Moka's more impulsive nature.
The Cullens from the Twilight series are obvious choices. They could interact with Harry in various ways. For example, Carlisle's medical knowledge and his calm, father - like presence could provide stability in a dangerous situation that Harry and Edward find themselves in.
Neville Longbottom is a wonderful character to add. He has grown so much throughout the series and can be a great support to the trio. Dumbledore, even if in a ghost - like or memory form, can offer his great wisdom. Also, Draco Malfoy can be included in an interesting way. Maybe in fanfiction, he has a change of heart and teams up with the trio against a greater evil.
Definitely Hermione. She's so intelligent and can offer a different perspective. She could help Teddy with his studies and give him advice on how to deal with the academic pressure at Hogwarts. Also, Ron. His sense of humor can lighten the mood. He could be like an older brother to Teddy, joking around with him and teaching him some fun wizarding tricks.
Hermione is always a great character to include. As a kid, she could be shown solving even more complex problems than in the books. Her intelligence and determination can drive the plot forward in fanfiction.
Definitely include Luna Lovegood. She has such an unique perspective on things. She could be the one who encourages Susan to give Harry a chance when Susan is a bit hesitant. Neville could also be a good addition. He could be in the background, being supportive of Harry's newfound courage to ask Susan out. And Hagrid, he could be the one who provides a special location for Harry to ask Susan out, like his hut in the Forbidden Forest.
Hermione and Ron are great to include. Hermione can help Harry and Ginny with their studies and also be part of their anti - Umbridge plans. Ron can add some comic relief and also be a good friend to both of them during this year.
Obviously, Harry, James, and Lily should be central. But Sirius Black would be a great addition. He was James' best friend, so he could provide a lot of insights into their friendship and the time they spent together at Hogwarts. Also, Remus Lupin could be included as he was part of their group. He could add depth to the story by sharing his memories of James and Lily.
Luna Lovegood would be an interesting character to include. Her unique perspective on magic could help Harry and Molly in unexpected ways. For example, she might know of some strange magical creatures that are relevant to a mystery they are trying to solve. Hagrid is another great choice. His love for magical creatures and his big heart could bring a lot to the story. He could help Molly and Harry take care of some new and dangerous magical beasts that show up in the fanfiction.
Hermione could be a great addition. She could be the voice of reason when Harry starts getting closer to Lucius. Her intelligence and knowledge of magic could also help in any situation they face together. Another good character would be Draco. Since Lucius is his father, it would add an interesting dynamic. Draco could be conflicted about his father's new relationship with Harry. And of course, Dumbledore. His wisdom and guidance could play a crucial role in how the relationship between Harry and Lucius develops.