Perhaps, then, the idea would be to start of a template that contains all the possible elements, which you can use to create a document from which you can delete whatever isn't required. That's much simpler than trying to selectively import content from another source. Alternatively or additionally, you might consider using Quick Parts/Building Blocks that you can selectively add. See:
http://office.microsoft.com/en-us/wo...010214071.aspx
http://office.microsoft.com/en-us/wo...010370568.aspx