Is there a way to create a mask based on UV islands?
you would probably need to create a texture to do that. wouldnt be that hard just bake a texture in blender or trace your uvs. though i dont really see the point since nothing outside the uv islands will be shown. unless your aim is to have each island as its own mask in which case that complicated things a bit but could be done via the methods above though again just basic texturing in the first place would probably work best.