You can hand-off character roles. Like, the antagonist in act one might be different from the character playing the antagonist in act two. I think this is actually done in the first Star Wars film, with Leia playing the role of protagonist in the first act, while Luke takes on that role for the rest of the film.
If you treat each novel as a separate act, then it will be fine for the characteristics to switch between the novels.
Also, if each novel is an individual story, then you don't really need to worry about the characteristics changing between novels. Darth Vader is a protagonist in The Empire Strikes Back, after being a contagonist in A New Hope. They're different arguments, and people can have different roles in different arguments. I might be a skeptic when I'm arguing about one thing, while I'm sidekick in a separate argument/story.