Very interesting work from @Zas, I only hope MB’s own database tag fields will be populated by more people real soon now …
Over the past so many years, I’ve been using fdemmer’s Last.fm.ng plugin quite successfully (with my own config.ini of course). Note this is not the same as Picard’s Last.fm plugin!
It already lets you specify a whitelist, categories, number of tags, tag translations, album genre fallback and whatnot and takes its data from last.fm. You can find my tagger script using it and the corresponding config.ini for the plugin in Repository for neat file name string patterns and tagger script snippets. I think it’s well worth a look and a deeper dive into its documentation.
A word of warning, though: Results can be horribly bad if there are several artists of the same name, like, say a pop group and a death metal band. You’d have to correct the genre and grouping tags manually in this case.
The plugin isn’t perfect, but it’s probably a good start until we can get more from the MB database. Be aware that it will slow down lookups considerably because of last.fm query rate limiting.