The main mask is currently a fusion of a mask-paint layer and a mask-fill layer. Some of the problems with it are:
- You cannot copy/paste/duplicate the painted strokes to a separate mask-paint layer.
- You cannot clear the mask, without deleting its children.
- You cannot fade out the painted strokes or give them a special blend mode.
- You cannot change the fill color (white/black) afterwards.
Would it not be great if Substance would create a separate paint and fill layer by default instead? You would get the exact same functionality using an already existing system, but without any of the limitations mentioned above. The concept of having a main mask could then be made redundant.
A more conservative option would be to give the user the functionality to convert a main mask into a paint layer + fill layer afterwards.