Hi Elliott, This is a great breakdown and very generous in sharing your process and insights, you came a long way from the vending machine days!
Are you planning on releasing the UE4 project to the public? Or only builds? I'd love to play around with it in the editor if possible!
Marmoset Toolbag 3 is gathering momentum and you could feel that at GDC 2017. Marmoset presented a nice video to highlight a sublime selection of scenes put together by some of their community’s best artists. Toolbag users are really pushing the limits of what is possible in real time rendering.
You can learn more about Toolbag 3 here.