workaround for opacity and mmre

hi, i often use the mmre to get masks of objects with defined materials for editing in post. the problem is that mmre do not support materials with opacity - i get a 100% white mask of the object, opacity is ignored.
my actual workaround is to change the vray materials with opacity with transparent max-materials, then switch to scanline renderer and render the desired masks for the objects.
works, but quite time consuming. whats your approach to this problem?