I just worked up a really long explanation but I think I need to do more testing before posting. Give me a few, possibly til tomorrow. In short I think you should add some 2D Graphic tags specific to the line types you want. Then assign those SketchUp tags to the actual lines within the 2D graphic. I don’t think ConDoc tags will work for line types since that is a direct product of the SketchUp tags.
Nothing wrong with using a hybrid system like you described…