I see that you never get an answer to your post.
I also was interested in understanding what exactly Tom Bayens meant in his execution modes docs I read in the wiki. I guess you understand it correctly.
We have a similar situation in our recent project.
The workflow as states and the business object related to the workflow has states. These have to be synchronized manually. In some event handlers or similar. In concept (4) the state of the workflow would be persisted directly to an attribute of the related business object. I wonder what exactly Tom Bayens meant here.
I have found this, which means a "yes"-answer to my previous post.
This would be a cool feature.
3) New will be an execution mode where the process state will be stored as one column in the users domain object. Imagine an Order class. With the PVM, you can deploy the process as a Java resource on the classpath and manage the state of the execution in a memberfield of the Order class. A special hibernate type can store this memberfield as a string column directly into the Order class.
But I wouldn't persist the process state as string to a member field of an entity, but rather make it configurable, in case one wanted to use an Integer or whatever.