Share options for a Linked Dataflow

You are correct in that for linked tables, they need access to the source.  What you can do in the same dataflow with the linked tables, is create a reference to the linked table (right click on the linked table and select reference).  This creates a computed table.  You can then add additional transformations in the computed table or leave as is.  Save the changes, and make sure you refresh and setup a schedued refresh for this dataflow.  Your users should now see the computed tables in the dataflow.