Sorry for the doublepost.
Could this plugin be adjusted so as to download fics written on wordpress? There are some.
Additionally,
https://forums.darklordpotter.net/index.php has a section called Work By Author, in which there are fanfics. However, these require having an account, with a minimum on 5 posts to view. I'd imagine downloading things from there would be difficult, unless the user would be willing to give their username and password to FFF.