Hi Skylaw! Nice description! I wish that you will be a satisfied user, finally.
You are right, the documents have space for development
, but imagine this is not only for Mercedes, but you get the same box and manuals for your Audi/BMW/Mini/Porsche/Saab etc.
Each brand has different models/HUs/options/setups, moreover these might change from MY to MY ... the Ideal Manual would be a VERY big book.
These units are built in by professional installers usually. They know the cars better than an AM manufacturing company. For them some words would be enough: "install it right before the CDC in the MOST ring".
After the first couple of ten installation, most of them could write a much better manual than the original one.