France is the only European country with an independent, working nuclear deterrent. That's a very valuable asset.
So I see thee points for a sensible French policy (big question mark):
1. They can use it to their advantage and offer to protect EU countries. What would they gain and what can they ask for in exchange?
2. They should not 'share' control of their nukes
3. They would not want that another European country develop its own nukes.