Apparently He Doesn't!!!!
I thought he was a Producer!?
Here is what he said-
http://www.ew.com/article/2015/06/10/game-thrones-martin-books
“ Meanwhile, other wars are breaking out on other fronts, centered around the last few episodes of Game of Thrones. It is not my intention to get involved in those, nor to allow them to take over my blog and website, so please stop emailing me about them, or posting off-topic comments here on my Not A Blog .Yes, I know that The Hollywood Reporter named me the third most powerful writer in Hollywood last December. You would be surprised at how little that means. I cannot control what anyone else says or does, or make them stop saying or doing it, be it on the fannish or professional fronts. What I can control is what happens in my books, so I am going to return to that chapter Ive been writing on The Winds of Winter now, thank you very much.
It seems like he is downplaying how much influence he has on the show in that statement, but maybe I am misreading it.
I think your summary of Stannis’ killing of his daughter as it relates to the scene with Brienne is a very likely scenario.
What if Shireen and Stannis die in the next book, and they’ve simply simplified the plot by killing them now?