I think the reading list plugin has a better chance of working on the paper white. :)

I also read 99.9% of fic off of A03 as well, though I use the Calibre plugin Fanfiction Downloader to download and if you have epubmerge plugin you can download series into a single file using Fanfiction downloader. (not sure if you're subscribed to fanfic_ebooks at LJ) I made a recent post about this new change to the plugin Fanfiction Downloader.