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!
Corona Renderer Tutorial: Saving Render Elements
In this tutorial the developers of Corona Renderer software show the basics of utilizing HDRI maps and using environment overrides.
© CoronaRenderer, 2015 YouTube Link