What I meant is that you make the clothing model with polygons that provide the structural connection a closed  button would provide, so bridge between two vertices of the button base stitches and two vertices of the button hole, and define groups named say 'button 1 closure', 'button 2 closure', etc. These groups then to contain each the polygon(s) representing the closure of their button. 

In the group tool you can select easily the groups, and hence the polygons, representing the closure of the buttons you want to open, and then delete the polygons, thus breaking the connection. It is not a matter of morphs, and when done properly it will not change the vertex numbering. The only change is there are a few polygons less. 

Zippers you could do the same way, defining a narrow row of polygons connecting the two sides. You could then box-select the polygons not to be deleted. Obviously this will not move the zipper, but that can not be avoided.