Since almost nothing is too good/expensive for nuclear detterence, WI the French decided to build a batch of Mirage 4000s to replace the IVs? It would be considerably more expensive than the Mirage 2000N, but the M2000N two seater has the range and performance disadvantages that come for two seat versions of medium fighters. I think the performance, especially payload/range, of a 2 seater M4000 could tip the balance for highest priority national nuclear-deterrence roles. Once the initial batch was built for nuke roles would follow on batches take advantage of the performance of the 2 seater for the night precision attack roles that saw the development of the F15E, F18D and Mirage 2000N from single seat fighters?