Adding a way to dynamically/programmably define/edit lists for metadata lookups will enhance the quality of documents’ metadata and reduce the administration requirement from IT people.
Create a custom list (vendors, Employees, projects, Customers, Departments, …etc.)
Attach The list to an ACL to grant edit rights to authorized employees (HR, PMO, Sales, …etc.)
Make metadata type that uses such list for data source.
This way PMO can add projects after approval so documents can be attached to them, and HR can add employees after hiring, etc.
If these lists are accessible through an API then modifications can be automated through other systems or through an N8N integration layer.
If Items in these lists can be linked to groups then only users within these groups can view or select such items.
If Items in these lists can have a name/ID and value attributes then entry and change may be more user friendly while workflow may be used to add the correct matching value.