I came up with a pretty good workaround that doesn't necessarily involve adding sweeps to your wall structure but utilizing the "split region" and "assign layers" buttons. This answers not seeing the sweeps in plan view, while also allowing you to see the base profile in elevation.
To do this:
1)Click edit structure of your wall: Add Finish layers for the base on both sides of your finish and set them to 0". In this case I made a material for the wall base and applied it.
2)Set your preview to section to activate the modify vertical wall structure buttons.
3)Click the "Split Region" button and hover the outside edge until you get to the designated height (4" in this example) and click. You can use the modify button after to adjust this cut.
4)Do the same thing for the other side of your wall.
5)Highlight the Wall base layer in the table so that the row1 turns black.
6)Click Assign Layer, then click inside the 4" region on the left side that you created.
7)Highlight the Wall base layer in the table so that row 7 turns black.
8)Click Assign layer, then click inside the region on the right side that you created.
Voila, you now have added a base layer within the same gwb layer. You're welcome.