If you know python, you can always write your own plugin.
https://manual.calibre-ebook.com/creating_plugins.html
I'm not quite up for a crash course in programming and python so I just use a combination of Job Spy plugin (scrub tags) and Calibre Bulk Metadata Editor search & replace (regex mode). I have a #freeform custom column to which I use to hold a copy of the original tags from the AO3 EPUB.
Note, I believe you can also use FanFicFare to download AO3 metadata and do the filtering via its personal.ini file.
Calibre is also capable of importing custom column data from the EPUB's OPF file (assuming custom column exists in the library and uses correct type and format) so another approach is to edit the OPF files inside the EPUB to add custom columns populated with your data in case you're writing in a different language.