@Walter Hinteler,
spiegel-online has an interesting interview with the head of the mason‘s lodge of St.Stephen‘s Cathedral, chief restoration architect Wolfgang Zehetner:
Wiederaufbau von Notre-Dame "Bitte keine Plastik-Wasserspeier aus dem 3D-Drucker" Reconstruction of Notre-Dame "Please, no plastic waterspouts from the 3D printer."
He thinks that it will take decades until the cathedral is rebuilt true to the original. This is mainly due to the necessary craftsmen, but also because, for example, trees of the quality that existed in the 13th century can no longer be found in Europe today. Also, the corresponding stones would no longer be available today from Paris and the surrounding area.
After 1945, St. Stephen's Cathedral was covered with a steel roof. Wolfgang Zehetner says that things had to go fast back then, and so the engineers had more to say than the preservationists.
A steel roof would be at least technically a very good solution - and not as costly as the original version.
In Notre Dame's view, it would be legitimate to choose a modern design as a replacement that would benefit the building in the long term, such as lower weight and greater stability.
However, a steel construction would not necessarily be safer: in the case of a fire with wood, you can estimate quite well how long it will take to burn away, and you can deduce from this how much time you have to save people, for example. Steel, on the other hand, which is heated so much, does not burn, but can buckle in a matter of seconds because it then becomes soft. So it is not the case that steel protects against all dangers.
Deutsche Welle has a video (in English) about the same topic with the same person:
Restoring Notre Dame