.. to add to Alex's post .. for Vmcg
(a) FAR25 is nil wind and I presume JAR/EASA25 is the same .. don't usually keep up to date with the latter
(b) UK BCAR D (replaced by JAR25 around 1979 ?) called up 7kt crosswind
(c) the basic philosophy is that Vmcg puts a line in the sand and there is no expectation that well behaved aeroplanes from polite society would be silly enough to spend much of their little lives in that area. As a consequence the probability of combining a Vmcg-limited takeoff with a V1 failure under strong crosswind conditions .. at aft CG, etc., is sufficiently low that the certification doesn't worry too much about it. Keep in mind that the Design Standards don't seek guarantees .. only that the calculated probability of catastrophe is very low .. not zero.
However, for some cases, especially short distance near empty positioning flights, it might be a consideration. I can recall one operator for whom I did some contract work which had a regular such positioning flight. In such circumstances it is useful for the pilots to realise that if they combine a min weight/speed takeoff schedule with a strong crosswind they perhaps exposure the operation to a risk which is unnecessary with (generally) a heap of spare runway. If, on the other hand, the runway is very short, then you either wear the risk or defer the departure until the wind abates a bit. Keep in mind that the increase in Vmcg is in the range 0.5 to 1.0 (plus) kt/kt with crosswind so, given that some aircraft have pretty high crosswind limits, it is worth keeping the problem in the back of the mind.
Vmcg is determined effectively for nil nosewheel cornering capability so, with the max aft CG, it very much emulates a wet runway failure case. However, I wouldn't plan on saving my neck by relying on cornering capabilities in the heat of the moment.