Think of it as a transparent matryoshka doll. Apply a the OCS to a block. Export those blocks within another proxy export. And render the top level with everything showing up as fully rendered elements. The idea is save on system resources. I had to work this way when I originally worked solely on a laptop.
A video of how it works here - Its like that movie inception.https://youtu.be/sQygBzsQ6Os
Essentially you could keep going deeper with the inception. Just save your layers and ocs's in different folders. I find if you put 2 ocs files into the same folder their assets can be duplicated if not named properly. I don't like leaving SketchUp either.