Why diversify? If you have enough power when you need it without emitting CO2 I would think that would be enough.

However, no new nuclear construction for that many years does look like a mistake as France looks like it is slightly increasing use of coal this winter: https://www.rfi.fr/en/france/20220112-france-fires-up-coal-p...

If France had more NREs it would still face the same issues without adding considerable storage capabilities (any big country that does 80% NRE thanks to storage?)