I might be arriving a tad bit late to the party but nonetheless a couple comments on Auteur Theory
- Whether or not an actual theory, this discussion seems to me pretty self-evident. Each director has a personal vision of the world – to what degree that vision extends is another matter – and as such their filmmaking decisions, preferences, and interests will reflect this vision.
- The need for consistency in actors makes little sense to me. What purpose this serves I am not sure unless the actor, like mise-en-scéne, camera techniques, motifs, etc., serves to reflect patterns in the artists work. Even so this add-on seems contrived.
- That’s about it with Auteur theory
To address the actor part of auteur theory…
This is irrelevant to the point you are making here, but on page 9 of Understanding Film Theory, the actor is listed as an potential auteur. I don’t necessarily agree with the argument presented here, but interesting to think that an actor could rise above the director as being considered an auteur.
To address your point of the actor being a mark of the director’s specific style, I think that you’re right in that the actor, like mis-en-scéne or camera angles, becomes a tool of the director. Richard Burton casts Johnny Depp and Helena Bonham-Carter in his films time and time again because he knows they will produce a performance that falls in line with his vision as auteur. In this sense, the actor, like any other cinematic convention, is a tool of the director.
Here’s an article about actors and directors who frequently work together:
http://mentalfloss.com/article/33665/13-directors-who-work-same-stars-again-and-again