Mask modifier for Grease Pencil

I propose a mask modifier for Grease pencil. The reason why? So you can specifically mask certain shapes by a target instead of within the GP object. The modifier method would be good so you can can move around and animate the mask as needed. I'm aware you can mask by collection but you have to use a 3D object which is fine, the problem is it blasts everything behind it away not good for viewport animation. Good for compositing