Wasili asked: to contact external renderer devs (no answer yet)
Roberto suggested: BEER must runs with blender, inside blender and have access to all its information and features. But leaves the current code alone, as much as possible. (All present in discussion agreed)
Create 2 new properties window tabs for
1. layering shader (object shading) and another for
2. world tab (sky/world/color grading/screen space effects)
that can accept the required BEER scene and BEER specifications, then consider that data from inside the internal model data when you press render.
The way blender stores data is very smart: it can allow for additional information to be stored with an object or scene, and the rest of the system will simply ignore it if it doesn't know what it means.
Get in contact with devs to shortcut the understanding of the code. But after we have done more code reading ourselves.