One common theme is friendship. Kevin and Gwen's friendship is often explored, showing how they support each other. Another theme is growth. Kevin's growth as a character, whether it's in terms of his powers or his personality, is frequently a part of these fanfics.
I'm not sure as I haven't read the story, but he could be the protagonist or an important character involved in the events related to the Christmas killing.
Among the Heisei Ultraman series, there were dramas like "My Hometown is Earth","The Messenger of Nong Marte", and "The Messenger of Monsters and Teenagers":
1 Supernova Era: Ultraman and the Galaxy Empire
2 " Night of the Galaxy Railroad "
3. Monster Messenger and Teenager
4. The Legend of Ultraman
5 Galaxy Guard
These series had a deep Ultraman element, but also added some light and humorous elements. It was a very popular Heisei Ultraman series.
A really interesting 'Ben 10 Kevin and Gwen' Kevin fanfic is 'Kevin in the Spotlight'. This fanfic puts Kevin at the center of the action. It shows how his actions and decisions not only affect his own life but also his relationship with Gwen. It has some great character development for Kevin and some really sweet moments between him and Gwen.
Since we only know about him from the title 'Kevin Cooper NY Times Magazine Interactive Story', he could be many things. He might be an activist whose story the NY Times Magazine wants to share in an interactive way. Maybe he is a local hero who has made a significant impact on his community, and the magazine is using this interactive story to bring his story to a wider audience. Or perhaps he is a person who has been through a unique experience, like surviving a natural disaster or overcoming a great personal hardship, and the magazine is chronicling his story.
It's difficult to say. Maybe there is a Kevin who has an idea for a war novel. Or perhaps it's a misnomer and there's no real connection between a Kevin and a war novel. There could be a Kevin who is interested in war and might write a novel about it in the future, but we don't have enough details to know for sure.