Some very interesting questions!
I cannot enlighten you regarding operating procedures, but I can tell you about testing.
Although of course you are correct that the ability to control the aircraft under such circumstances varies with crosswind, as far as certification is concerned Vmcg does not.
Vmcg testing is always conducted under conditions of less than 5 knots. There is no time delay built into the test, and so reaction times will typically be of the order of half a second. Testing is always conducted at aft CG (worst case).
Therefore the Vmcg quoted will theoretically be for the 'worst case', but does not take into account any crosswind, I guess the theory being that in the unlikely event that you have an engine failure at this speed it is too difficult to account for the fact that you may also have a crosswind.
There are certainly some within the test establishments who have felt uncomfortable with this, but as far as I know these are still the rules for certification.
Hope this enlightens at least a little bit!