metadata is a very bright point of Pydio significantly better compared to all other software out there.
Providing extensibility to the metadata system is really a game changer.
At some point, this could be interesting to provide a way to translate terms. This could be front-end only, and based on a user-provided javascript/json/gettext file.
Another aspect would be to provide (plugin’s developers) a way to make namespaces and metadata more dynamic.
Eg: Adapt tags according to the filename, extension, uploader or guess some possible terms from exif or from an external API, set default some tags according to some context & conditions, … …
There are many possibilities one can think of, but they all depend upon being able to programmatically alter the metadata of a file and somehow alter the widget (HTML & javascript) of the metadata box.