An important addition to standard business events catalogue could be a Document management business event. The business event should be linked with a document type (ex business event should not be triggered for the standard <> document type but only for an exportable <> document type).
It should be able to provide either a shared access signature to the attachments or even to clone some important files to a customer storage account. A similar setup for the storage account already exists for the personnel management integration which could probably be reused.