Interesting points, fu, and which triggered the following thoughts in my head:
Perhaps part of your stance is predicated upon the assumption (which you make KNOWING it's actually false) that the character exists already but is not known to you -- that is, their traits and personality are not things which you craft but things which you discover as best you can (I know, that's pretty much exactly what you said, but bear with me).
This assumption (fascinating in its anti-rational nature) makes for an interesting light in which to study the Stances defined in this thread.
The Pawn stance, for instance, requires sufficient knowledge of the character in order to employ that character in assorted strategies. It follows, however, from the "fusangite assumption" (I'm going to make that term standard terminology if it kills me) that any such employment of a character is likely to end up non-optimal since so much of the character is unknown.
Well, sort of. The Pawn stance (in it's most extreme form) requires so shallow an understanding of the character that it's probably not a big deal. Onwards.
The Actor Stance seems at first to be deeply problematic for those who operate under this assumption. How can you "play" a character whose basic nature is unknown to you? From what vantage point, if you are playing the character, can you
observe the character in order to discover its nature? Can one observe and act simultaneously?
But on consideration I don't see why not. We do that ourselves, don't we? I mean, I wouldn't say I have a perfect grasp of MY own nature, so why would I have such a grasp of my character's? My own personality is something I have discovered over the years (often to my deep and bitter disappointment). So perhaps the Actor stance isn't as problematic as it seems -- in fact, it becomes MORE "realistic" or "deep" if you adopt the fusangite assumption.
How about the Author stance? Well, in my mind this stance isn't, let us say, mutually incompatible with either of the other two stances. That is, one can make choices on a "story" level (which is certainly something I do) while still operating within a Pawn or Actor stance (at least, the Actor stance that's been redefined to be self-observant as above).
Again, isn't this something people do every day with their "real" characters? I know I've often done things because they seemed more exciting, more likely to turn into interesting stories. I got my English degree and narrowed my choices down to teaching in Japan or going to law school. I chose Japan because it seemed more likely to turn my life into an interesting story.
Well, that, and I met some lawyers.
So I don't see that the Actor and Author stances are incompatible -- a realisation I came to when considering how the fusangite assumption (is it working yet?) intersected with the Sweeney Stances (huh? huh?). You can be taking an Actor stance, be immersing yourself in your character, and STILL be making story decisions or discovering your character's inner nature as play proceeds. In fact, maybe it's arguable that if you AREN'T doing those sorts of things, you aren't taking a very interesting position on the Actor stance...