In Picard, I think this sort of thing can be done using a tagger script something like (untested code):
$set(artist,$replace($%artist%,[unknown],[your translation of unknown]))
$set(artist,$replace($%artist%,[anonymous],[your translation of anonymous]))
$set(albumartist,$replace($%albumartist%,[unknown],[your translation of unknown]))
$set(albumartist,$replace($%albumartist%,[anonymous],[your translation of anonymous]))
$if($eq(%title%,[untitled]),$set(title,[your translation of untitled]))
As for “Various Artists” and “standalone recordings”, these can be set in the Metadata Options settings page in Picard.
Of course, this will only use whatever you have entered, and not be different for each different release language or selected user language.