You could do it but even as a person who likes hybrids I wouldn't recomend it. Other than Eastern Milks and fully mature Black Milks, all the other milk snake subspecies have the same basic adult pattern and the offspring will just look like milk snakes but will be impossible to identify becuase of the mixed characteristics of the parents. If you want to make something different try crossing a milk with a king or a corn snake, it's more difficult but the resulting offspring do not look like either parent and can easily be identified as a hybrid.