Ben's character could also be developed through his interactions with other rangers. He could learn new techniques and skills from them, which would make him more versatile in his ranger duties. At the same time, this could also lead to some friendly rivalries. For Summer, she could participate in Pokemon contests on the side. This would show her multi - faceted personality and also give her a chance to bond with different types of Pokemon in a non - ranger way, further developing her character.
For Ben, his character could be developed by giving him a personal Pokemon that he has a special connection with, like a Pokemon he rescued as a baby. This would add more depth to his character as we see his softer side when it comes to this Pokemon. For Summer, she could be given a backstory about why she became a ranger. Maybe she had a bad experience with Pokemon poachers in her childhood and that's what drove her to protect Pokemon.
To develop Ben further, he could face a moral dilemma in a fanfiction. For example, he might have to choose between saving a group of common Pokemon or a single very rare Pokemon. This would force him to think about his values as a ranger. For Summer, she could be put in a situation where she has to lead a team of new rangers. This would test her leadership skills and also show how she has grown as a ranger. It would also allow her character to develop in terms of responsibility and decision - making.