I sympathize with you about what seems like a simple enough function.
Graphisoft could implement the LightWorks Sketch Engine that would address color and edges as you like.
However, something like this is easy enough to do in two steps, merging a solid OpenGL view with a squiggle line rendering in Photoshop, leaving you with all sorts of great editing filter options.
Don't say that you don't have Photoshop? Pity.
The attached is jus a rudimentary example.
Dwight Atkinson