In response to a query about a bug and extending the RSS capabilities of Drupal, one of the developers posted the following note about future improvements to import.module:

You really need to look at the import.module in Contrib. It is so sweet. It stores incoming feed items as nodes. That means you can queue, promote, etc. these items just like other nodes. Further, feeds can be associated with terms, so that every item that comes in under this feed will have some default terms attached to it. Thus, you can easily accomplish what you are talking about (mxing external content with your own) without bothering to import your own feeds. Just browse to the appropriate term(s) page.

The import.module in Contrib needs to be updated a bit and Dries posted some concerns which must be addressed. He also posted that he likes its ideas, and would accept it into Core when it is ready.