Here's another workaround for 2d shapes to scale in LayOut:
Do all your drafting in SketchUp on the XY plane.
Import into LayOut,and choose the desired scale.
Render the model in vector, then use the "explode" command to convert the SketchUp model to LayOut native shapes.
Depending on the complexity and overlapping of your shapes, you will have some level of cleanup (joining, splitting lines, etc..).
But then you have LayOut shapes, to scale, and you were able to draw them relatively quickly in SketchUp.
I realize this isn't exactly what you were going for. I've really wanted the same functionality in LayOut (and the guides tool, and the tape measure tool). This is how I've approached similar situations.