I've been playing around this for a couple weeks and wanted to share. I wanted so badly to store the games on my NAS on a single file each, in order to save some space and not having hundreds of file around there.
So, I though about having a zip (or 7z, or whatever) using a fixed structure, the same that RPCS3 uses internally on its HDD so I could just unpack the file right over the RPCS3 folder just before launching the game. This way I can have in a single file the game with every patch/dlc that I want, ready to just unpack and go.
This way, every archive has this basic structure: