While I am sure others have uses for this as well, for me I run a Super Hero game where people and objects get blown through walls or incinerated sections. So I propose an eraser or scissors that will allow the draw lines to be either cut and deleted between or much like GIMP dynamically erase the line. Given that when a line is on the lighting layer it processes with the Dynamic Lighting and Movement System being able to affect the lines in this way would allow simple changes that would allow for reactions to player effects to the world.