Finally, a few months ago, we spoke to our favorite contractor about building the closet. He said, much to my delight, "if you're going to the trouble/expense to add the closet, it won't be much more money to make a sitting room too!". Now, if I had suggested that, I don't think Ed would have been so agreeable. It does make sense though, so...this is what we designed. It's a new closet AND a sitting room.
This is the door from the MBR into the new space. We removed the window and it is now in the new sitting room wall.