Hi,
If the structure keeps the same, and if you keep in charge of the db accesses, can't you simply add other columns like userID to your table and keep them hidden to your users?
Then for sql text queries, you can try playing with RetrievalQueries and FetchDataReader, which you could even combine with projectors to your main entity.
The last solution would be to change the presistenceInfo objects at runtime. That would probably involve making the PersistenceInfoProvider Public in the first place, then add new mappings and change the entity/entityfields properties such as "ContainingObjectName" with probably some more plumbings. I can't tell you the exact procedure.
I would go for the first solution if possible...