I would love to see the "Album Artist" Tag Implemented. As someone who has a large amount of Compilation Albums, browsing via the current "Artist" Library page is simply not usable.
This is because for albums such as "Ultimate 80's" for example; under the current "Artist" Library page would list every Artist that has a Track on the Album. This is obviously not helpful, especial when you have several or more compilation Albums, as this view soon starts to show 100s of Artists that have one or only a few tracks.
Implementing the "Album Artist" Tag would change this to a much better situation as these Compilation Albums would all be listed under the "Various Artists" which they are usually tagged as (by default using musicbrainz to tag) under "Album Artist". This could even be implemented in such a way that "Artists" Library View checks for "Album Artist" Tag first and use that, if no "Album Artist" Tag is found then check "Artist" Tag and use that, if no "Artist" Tag is found show as "undefined".
If Implemented the above way it would not effect people who do not use the "Album Artist" Tag, but would be a much Improved View for those who do.
I have seen comments saying that the problem with "Album Artist" is that MPD seems to ignore the tag. While that may have been true at one point i believe that the "Album Artist" Tag is Now Supported by MPD as it is listed on: https://www.musicpd.org/doc/user/tags.html
Another reason I believe this to be true is that by running the command "mpc list albumartist" on my RuneAudio Device it successfully generates a correct list for the "Album Artist" Tags.