Restriction to have a legal copy is a bit stupid. I mean really, it is obvious that the best testing will be from DKS users, since they played it and can notice the bugs easily. But who in the sane mind would buy the same game TWICE?
I think you need to change the way hot users can test the patch. Just because you REALLY need massive testing consider the fact how buggy Div2 patches was :P Otherwise, you get another buggy patch, just more HUEG.