This will allow anyone the ability to edit/add masks within CTA without concern of exporting a non exportable version and without increasing file size.

Hopefully soon the marketplace will also support exportable CTA products and the masks upon export will be added to the prop psd layer or whatever the export condition is.

This should make it easier paint in a river shape or shoreline on an imported video of water, ocean etc with a custom animated mask shape.
If possible it would be useful if the mask optionally provided feathering to blend in with other scene elements.