How to use JAudiotagger to delete nonstandard tags?

Question

The problem:

My audio collection, which contains mostly FLAC but also some MP3 and maybe a few OGG files, is sourced from 1) ripping my CD collection to disk and 2) purchasing downloads. My music collection looks like artist/album/{audio files,cover,liner notes}.

For some years I have been unhappy with the hot mess that is the range of audio tags in these files, caused by uneven data quality in things like MusicBrainz and also coming from providers of downloads. I've been writing a series on using Groovy on opensource.com and, having learned about JAudiotagger, decided to write some Groovy scripts to do a cleanup operation.

After some testing, I've come up with the following Groovy code to deal with my tags:

new File(musicLibraryDirName).eachDir { artistDir ->
    artistDir.eachDir { albumDir ->
        albumDir.eachFile { contentFile ->
            if (contentFile.name ==~ /.*\.(flac|mp3|ogg)/) {

                // Get the tag body

                def af = AudioFileIO.read(contentFile)
                def tagBody = af.tag

                // Save the values for the known and wanted tag fields by FieldKey

                def album = tagBody.getFirst(FieldKey.ALBUM)
                def artist = tagBody.getFirst(FieldKey.ARTIST)
                // etc

                // Get a list of all the tag field ids

                def originalTagFieldIdList = tagBody.fields.collect {
                    tagField -> tagField.id
                }

                // Delete all the tag fields except VENDOR by tag field id

                originalTagFieldIdList.each { tagFieldId ->
                    if (tagFieldId != 'VENDOR')
                        tagBody.deleteField(tagFieldId)
                }

                // Set only the non-blank saved wanted tag fields by FieldKey

                if (album) tagBody.setField(FieldKey.ALBUM, album)
                if (artist) tagBody.setField(FieldKey.ARTIST, artist)
                // etc

                // commit the changes

                af.commit()
            }

        }
    }
}

I have run this on a "test music directory" and as far as I can tell it seems to do the job, but I have two main concerns and I'm looking for advice on them:

1. Is this a good general way to approach the problem, or am I completely missing something here? My concern is that saving the wanted tag fields by FieldKey, then deleting all tag fields by tag field id, then re-establishing the wanted tag fields by FieldKey again seems kind of heavy-handed or inefficient or something ugly like that.
2. Though tagBody.delete(tagFieldId) seems to "delete tag field by tag field id", this seems wrong, given that the interface doesn't define such a method and although AbstractTag does, though it's protected, and FlacTag doesn't extend AbstractTag but rather uses composition to define its internal tag property as VorbisCommentTag which DOES extend AbstractTag.

Any critiques, advice, suggestions much appreciated.