The Vault add-in to Inventor should have an API exposed so that it's features can be driven by 3rd party applications.
The main reason for wanting this functionality is to allow 3rd party programs to add Inventor files to Vault. This is currently not allowed with the Vault API, Autodesk recommend letting the CAD plug-in do the upload of CAD data.
For the same reason, Vault add-ins to other CAD programs such as AutoCAD should also have an exposed API.