> * takes care of album art for various values of "takes care"
What do you mean by that?
There are plugins that:
* fetch missing album art
* embed the art in the track file
* extract the art from the track file (to save as cover.jpg etc)
* resize the art
emms-tag - Use the beet command line interface to beets from Emms
to correct and update track metadata. One interesting issue which would
come up here is that the underlying services, such as
acoustid/chromaprint, are licensed only for non-commercial use. So while
the software is free software, the services are not. People will have to
go through the process of having beets working with fpalc (the FFT
component of chromaprint).
Two remarks:
1. The default tagger uses musicbrainz and not the acoustid/chromaprint mechanism (which, as you indicate, is not so straightforward to set up).
2. The command line interface to beets is interactive if the match to musicbrainz metadata is not 100%: the user is offered choices to accept/reject. So a putative emms-tag would need some UI to handle that (unlike metadata extractors like tinytag or exiftool).
---Fran