I am interested in what your final solution was. Please share when you have time.
I created a wall type form the 2X4/Brick wall, and just made the stud 1" thick. This allowed me align the inside of the walls with each other and create the correct thickness I wanted to show in 3D. Then I added a concrete material cap to the wall type and made it wide enough so that when I aligned the walls together it has a 2" overhang on each side. That way it draws the cap with the wall, and there's no need to try to create it separately.
When I aligned properly they appear as 1 structure in the 3D model. I created a drawing called "top of structure" and put the walls there. Then checked "Rake top" and clicked the multi height button and entered some random numbers to just get started... then tweaked it until I had it just right.
So If you look really close in the side view you can see where the brick texture is misaligned where the wall type changes... this is only noticeable if you zoom in.
The flat wall is 24" long, 24" tall. Then I started a new wall connected to that 2' tall on the left end, and 12' tall on the right end, and it gave me very close to the 9/12 pitch to match the roof.