This idea is a similar system to the style synchronisation feature in AutoCAD Architecture.
So you working on a project with several models, how to you make sure that a certain door family is the same between all models?
At the moment the only method you have is to save out the family and then load it into the other models - or use transfer project standards.
What I would like for the user to set up a project as a Project Library which hold all of the Families. the library would track the versions of the families.
When a building model is loaded, the feature would automatically scan the project library and notify the user if the version of a certain family has been updated in the library, the user can choose to load it into their model.
This way families can be consistent between all of the projects, and when a family is updated it will synchronise out into the individual building models, and the users can be sure they models are always consistent and up to date.