I don't think replacing the windows or letting in sunlight would work. I agree that the lighting system should go, but the design and use of stained glass in th

I don't think replacing the windows or letting in sunlight would work. I agree that the lighting system should go, but the design and use of stained glass in the middle ages had several purposes, one of which was that the light was a visual representation of God's glory. In the Medieval period there were long-running discussions among theologians about light's divine significance (https://books.google.com/books?id=eXbDBwAAQBAJ&printsec=frontcover&dq=species+of+light+medieval&hl=en&sa=X&ved=0ahUKEwjAlv6b_MXiAhUSRqwKHW6ID8kQ6AEIPTAE#v=onepage&q=species%20of%20light%20medieval&f=false https://books.google.com/books?id=eXbDBwAAQBAJ&printsec=fron...). Natural light might be beautiful, but it is transposed through the use of the glass into a wholly religious artifact. You can even "touch" this visual representation of divine beauty by running your hands under the reflection of colored light. And anyway, it's much easier to examine the stories embedded in stained glass motifs with light coming from the outside in.