The glass roof is not a bad idea. It would be very French to do that. Like the I. M. Pei pyramid at the Louvre. If it's done, it will be done competently. So many people are watching.
Please, no. I am sick and tired of this international-style glass and steel business. We have plenty of buildings painted from this rather dismal palette. I'd like to see Notre Dame restored using traditional materials.
Wouldn't that drastically increase the sun exposure on the internal elements and artifacts in the church? Sun damage is noticeable in just a few years, let alone on a time scale of centuries...
That would simply create a gigantic greenhouse that would require enormous energy inputs to keep it habitable during most of the year. Not the most eco-friendly solution.