Why don't you add the ID3v2 feature? It's already included in TagLib 1.3.

(we can't see new fields). Or maybe you should allow to 'force' to id3v2...

I should explain myself. I could be great to be able to upgrade a file from id3v1 to id3v2, to be able to display and sort the collection with the fields only available in id3v2.