Then explain what you meant by:
a similar one for FLAC AlbumArtist would be adequate to solve the current problem.
E.g. this proposal
Format-independent album artist
/t/8874/1
... an Album Artist placeholder that works across all formats i.e. translates to
%BAND% on WMA and MP3 and to %ALBUMARTIST% on FLAC
Other than Mp3tag mapping its BAND to FLAC's ALBUMARTIST,
I have no idea what else it could mean.
See the above.
You immediately run into two problems, just to start:
How would you actually write a BAND field?
I suggest %band% - unchanged.
What if you need to use 'ALBUM ARTIST' (which is used by foobar2000) in FLAC files?
That is separate from the current problem. I agree that is needs consideration but better in a separate topic.