Really amazing vision, Matt.
thanks for the inspiration.
btw: have you played around with tricks in post, rendering out surface ID and surface normal passes? You then take them into post and run a 'find edges' filter on them. It may not be applicable to what you're trying to do, of course. (you can even run a depth path and use it as a mask to clamp out the regions you don't want the line tracing effect).
-m.