When you earn my trust, I will take a bullet for you. When you lose it, it takes a loooong time to earn that trust back.
For the "I wish you would write a fic where..." thing: In a canon setting, except Stiles is older, went to highschool with Derek and was friend with him. He can be a deputy at the beginning, trying to deal with a newly bitten Scott, whom he considers a little brother, and the return of Derek, his friend from school and old (current) crush. Do you think it's a good idea?