Hi Susan,
Thank you for your question and great considerations and analysis. My question would be, what is in the rest of the room? What other elements have you represented? I do believe the purpose or essence of the window, to bring in light, would trump the fact that it is made of glass.
Having the natural light flow into the room is great for space clearing as well. A dark room with little sunlight has a tendency to also have dark corners that create char qi. Sunlight helps open the space.
All the best!
Kat
