Hi Wynter Nyght.
We almost went that way with ArtRage instead of having standard layers. It's a good suggestion.
In the meantime here's something you can do which is sorta like it...
Create a new painting - choose one of the standard white papers.
Add a new layer.
Edit the paper settings of the new layer to make the paper 100% opaque. (So now you have two layers with opaque paper).
Now whenever you add a new layer, the new layer will have the same opaque paper white paper as the second layer.
When you sketch on a layer, you can turn off all the layers above, as though they were pages of paper above.
It's a little slow to show and hide layers in ArtRage 2.2, but we're making it faster in the next version of ArtRage.
AndyRage's mantra for graphics engine code:
"Sure - how hard can it be?"