Perhaps a female soldier who catches Stiles' eye. She could be a skilled combatant and have a complex personality. Their relationship, whether it's a friendship or something more, could be a major part of the story as they both navigate their military careers.
Another main character could be Stiles' best friend from his pre - army days who also decides to join the army with him. They would support each other through the tough training and face the challenges of military life together.
There could be a tough drill sergeant who acts as a mentor and a source of conflict for Stiles. This character would be strict but fair, and would push Stiles to his limits.
Well, one possibility is that Stiles could be facing some inner turmoil at home or in his personal life, and joining the army becomes his way to find purpose and discipline. He might start as a clumsy recruit but gradually grow into a strong and reliable soldier, making new friends and facing various challenges along the way.
In many 'Stiles is not human fanfiction', Malia could play a significant role. Given her own complex backstory and her were - coyote nature, she might be able to relate to Stiles in some ways if he's not human. She could either help him adapt to his new state or be in conflict with him. Kira could also be involved. Her kitsune powers and her kind nature might lead her to try and understand Stiles. And the Sheriff, Stiles' father, is bound to be in the story. His relationship with Stiles would be put to the test as he discovers his son is not what he thought he was, and he'd have to deal with his own emotions and the potential danger that Stiles' non - human nature could bring.
There could be other members of Peter's pack such as Derek. Derek often plays an important role in stories related to packs. He might be initially skeptical of Stiles being part of the pack.
Well, aside from Stiles, Scott is bound to be a central character. Their friendship is so strong that Scott would immediately start looking for ways to rescue Stiles. Derek Hale is another likely character. Given his past with the alpha pack and his relationship with Scott and Stiles, he would have a role to play. Then there's Allison. Her family's history with the supernatural means she has skills and knowledge that could be useful in rescuing Stiles. She could be involved in the search and rescue operation, using her archery skills and knowledge of the supernatural world to help out.
Another possible main character could be the base commander. Let's say Commander Smith, who notices Bella's potential and gives her special tasks or opportunities, which then drives the story forward as Bella has to prove herself worthy of these tasks.
Luna Lovegood would be a great pairing. She's quirky and open - minded, and her unique perspective could complement Stiles' inquisitive nature.
Stiles' father could be a major character. He would be worried sick about his son and use all his resources to try and find him. Maybe he teams up with some of Stiles' friends like Scott or Lydia.
Another character he could interact with is Thor. Thor's otherworldly nature and his powerful abilities would be quite a contrast to Stiles. Maybe Stiles could help Thor understand some earthly concepts while Thor could teach Stiles about Asgardian culture and power.
A group of misfit soldiers could be main characters too. They are all a bit different and don't quite fit the typical military mold. But together with Harry, they form a unique unit. There might also be a high - ranking officer who takes an interest in Harry's progress and either helps or hinders him depending on the situation.
Perhaps he feels that the other pack can offer him more opportunities for growth. In some fanfictions, the new pack might have access to different kinds of magic or knowledge that Stiles is eager to learn. So, he joins them to expand his skills and understanding.