This assignment was intended to allow students to consider what it would be like to be one of the characters from the novel and write a letter to another character.
My wife's original assignment includes two options. I added a third that allows students to become characters that do not exist in the story, like someone's wife in the future. I did this mainly because my experience as a teacher showed that students were unwilling to accept the sins of characters and think they could or would do the same thing, but they were willing to consider a friend, family member, or future significant other who had a shady past... go ahead and use that technique in some of your assignments, and you'll see a difference. It's also hard to make the assumptions my wife made about characters changing, but someone who was not an official character could see things from a more suitable perspective without being as fully removed as the readers.