OS:
You bring up an interesting point, while Vr and V2 are limited at 5% and 10% above the configured Vmca; V1 is only limited by Vmcg with no "pad" to cover the pilot. And, as several knowledgeable types have noted, Vmcg demonstrations for the regulatory authorities are pretty much a circus act. The pilot knows it is coming, there is no allowance for reaction time and all things are favorable. The real world pilot, on his 14th hour of duty doing a take-off on a 25m wide runway (I've been there) is really "on the edge" if one donk quits at V1 where Vmcg was limiting.
GF
Oh, and there is a 10 knot crosswind on the failed engine side, which isn't computed for in any civil charts.