What you are missing is the ambient light feature. It’s a basic feature of the most render engines since years. I missed it too, since it’s a method to get fast&clean results. (My favorite method if I use Octane for animations, since the method is so fast.) It’s a GI fake based on ambient occlusion.
This feature should be easy implented, I suppose so only a few lines of code need to be added to the scene description output. (So far I know from the render plugin AIR and the renderman language)
Here you see the options at Vray for C4D:
For example I was working on an air plane interior. Rendering the still images was no problem, the render time was ok, but my client ask me for fly trough animation and I got a problem. Some one help me to render the animation at Vray for 3dsmax based on ambient light.
For now you could work with invisible area lights. Some times it looks better if you disable “cast shadow” for the ceiling material and place the area light(s) above the ceiling.