[simias]

The spire that collapsed had been inaugurated in 1859, so it's relatively recent compared to the age of the cathedral. I don't really have a strong opinion on the subject but dismissing modern architecture as a whole before we've even seen the first proposals doesn't seem very... constructive.

[kakwa_]

1) The spire rebuilt in 1859 by Viollet-Le-Duc didn't have XIXe century look, it was heavily inspired by the one of the Orleans cathedral

2) Even with that, Viollet-Le-Duc is somewhat criticized for it's restoration works as he generally chose what looked "nice" as opposed to historical accuracy or significance.

Rebuilding the spire in a modern style would be a mistake in my opinion, or at the very least, a huge risk of style disunity of the building, rebuilding in Gothic style maybe boring but it's safe.

As to which technics could be used, that's another matter. Notre-Dame would not be the first cathedral to be rebuilt using the technics of the day.

Reims was rebuilt using concret, and the result is actually quite beautiful:

https://img.aws.la-croix.com/2019/04/17/1301016385/charpente...

Others were rebuilt using steel, Metz Cathedral for example.