If I wanted a game of thrones fanfic. The couple of things that I would never do is pair canon with OC. Second, if the characters were going to die later in the books then I wouldn't want to change that. After all, if the characters are die then it's going to happen anyway which no body can change that. Plus, I wouldn't change the whole story. I would just leave it the way it is, and figure out a way of how am going to fit my character into the story without inferring with other characters, or make changes.
Anyway, I would like to change the topic now, and just continue with my search for a fanfic writer. Since, you mention about the author of not liking fanfic then I would have no problem in choosing something else.