We should be able to make line-based families do whatever we want. Straight lines are too limiting. This could be accomplished by sketching the path of the line, using whatever drawing tools we want.
My particular application for this is for flexible lighting, but I'm sure it has other applications.
It would still be important for Revit to calculate the total length of the line. This way, for the flex light application, I can calculate the total wattage.
Others, please respond with additional applications so we can get some broader support for this.