But if she or David wrote and directed one episode, they would have to move away from other episodes, and there are only 10. Mulder and Scully need to be in all of them at full capacity.

Why that? David wrote and directed episodes with the both of them fully present. He also did it with Californication and Aquarius. Gillian directed a short movie and played in it. They totally can do both. Gillian used to say a lot she would love to write and direct more, I think it was the perfect occasion and it seems like it won’t happen. So I don’t know if CC’s such a despot that he refused that she writes one or if It didn’t even cross Gillian’s mind. We’ll probably never know, but that would have been one more episode written by a female writer. A good one, and a legit one.