A true restoration should be the default strategy at this point unless someone can come up with a compelling design that is overwhelmingly beautiful. That may be impossible but it's a least a fun thought experiment. To my knowledge, Notre Dame in modern times remains an active participant in Parisian religious and civic activities. Historic but still at work. For that reason, I think it's worth considering how it can be renovated into the current image of the city, as cultural views on religion continue to change.