Feature Request : roughing out and cleaning up on the same bitmap layer

With the new bitmap layer. I was thinking it could be nice if it was possible to Rough out with a colored pencil and clean up with a black pencil and erase the coloered lines on the same layer. like using Chromacolor animation pencils on paper. or like plasticanimationpaper had integrated
http://plasticanimationpaper.dk/
-Mads