Mask Node for Cycles

Cycles allows you to use simple gradients could we also use Blender's Masks as vector sources to derive gradients?

I have been making false perspective animations with image mapped planes, using offset parallax mapped but I need to animate masks on the images based on their 3D view.

Could it be possible to use Blender's Mask tool as input to Cycles nodes? I could still use the UV/Image editor to draw over the texture source there? Or could I load the source image into the MCE and animate the mask over time?

I guess that the problem is that the Mask is produced "after" 3d image drawing but before post processing? That is why Masks are available to the VSE and compositor?

I think that this would be a very beneficial tool for Cycles as a Motion Graphics device. I'm not sure if the same functionality could be incorporated into Eevee? That would make Motion Graphics production blisteringly fast.

Thank you for reading