I think that if Franceicon had used the "kill switch" (if it ever existed), they would have committed a sort of political and commercial suicide in terms of arms sales.
Who would have ever bought a missile or a complex weapons system from them ever again?
Better not to have anything like that, I guess.
In case the Exocets had been used against them, they would have known the right countermeasures. But I don't think the "kill switch" existed.
Maybe I'll be proven wrong soon...