I'd really like to, e.g., be able to write a script that updates files already picard-tagged without requiring me to open up Picard and navigate the GUI (basically, a quicker update-only script). I could use e.g. python-musicbrainz-ngs, but I'd have to rewrite all the tag-writing and mappings myself, which could easily and quickly fall out of sync with Picard.

Instead, I'd really prefer to be able to just use Picard's "backend" code as a library. Not sure how much rearchitecting this would require, or if it's even possible, but I thought opening a ticket was the thing to do!