It's called reciprocity...
My advice would be fucking simple. This thing wants no good to the russian federation peoples, as such, this thing must answer the federation.
Of course there will be private and public security services standing in the way to get this "french billionaire supporting a russian child rapist".
I don't think it's too hard to breach, as the fundamental goal isn't to get an extradition, but a warning.
Or more exactly a message...
ie, death squad, drive by with modern weapons to get the "fort" of the billionaire... I like too the surface (sea/sub) missile to get the jet in the air over an ocean... I find it fun too !
or the vacay island, the yachts... so many ways to tells those "rich, powerful and above the laws of nations" that they will always be at the mercy of the laws of war.
so what france shall do? what would be reciprocal? is abramovitch still protected by the child rapists uk gov? why?