There are some ways you can get pretty close to what you are showing,
The column tool will attach itself to a wall, making a projection in plan and a gap in the non-core skins in elevation. It can be incredibly useful for leaving a gap in the drywall, at the top, middle, or bottom of the wall.
With this, you could leave a gap at the bottom of the wall, then you will end up drawing in the top return of the wainscot in 2D.
I've found composite to be incredibly useful in plan views. They can work in sections as well, but you need to be comfortable with columns, beams, and SEOs as well to make them really shine.
Tom Waltz