Have an ACTION in the workflow TRANSITIONS, so when changing a documents state will either SHARE TO or UPDATE FROM Buzzsaw.
For example:
Custom Workflow State: Share to Buzzsaw
When a document is set to this state, the document is shared to Buzzsaw and also is LOCKED within the Vault.
This will make the process easier to share a document to Vault, but also have only one (1) live document that is allowed to be edited.