JohnT--
Thank you for the compliment on my suggestions.
I agree that you and Marc would fit into the sphere of strategic culture as would Mr. Nagl and Ms. Flournoy.
My rule of thumb is that if one's goal is to advance the understanding, discussion and formulation of policy, I'd be inclined to think that person is situated in strategic culture. If one is looking to advance a political agenda and to trade horses, one's in political culture.
As noted, the spheres overlap and one's position can shift over time or on a given issue. All four spheres bring something to the table. (For what my two cents are worth, I have questions about the CNAS that will be answered over time.)