Adding a datablock to store properties per file (proposal)

Blender is currently missing a way to store properties per blend file, without being tied to a scene. Right now if we want to register some custom properties (that aren’t related to objects) we have to store in the scene. This has the drawback that those properties can’t be shared across scenes.
The only datablock we can use “globally” is the window manager but the values of those properties aren’t saved in the blend file.

I propose adding an empty type in, something like or The only use for that datablock would be a storage place for addons, for properties that don’t need to be coupled with scenes/objects/etc.

What do you guys think?