A different idea: seems like we could view this as a classification problem, no? How about shipping a category tree that the system could utilize to classify content as it is added to the content repository?
Content -> Text -> Uploaded|Generated
Content -> Binary -> ...
or something along those lines. Haven't given the tree any thought but clearly you could imply quite a lot by selecting a category from a well-organized tree. The subsite could use this information to act appropriately on new content.
