I am a strong believer that the quality of a man is defined by his choice of enemies. So let the stripey-socks have metal. It's dead for innovation, and has all but returned to its status of yet another youth tribe, just as it was when Iron Maiden inherited it. Death metal's subversive groundwork has been virtually wiped out by a decade of over-exposure. The badge is not one of honour. So move on, and take what is now deserved. The technical, theoretical bands that base their work on musicality should be called classical. If the classical snobs hate this idea, good! Debating with them instead of internet drama queens makes the stance appear so much more credible. And if it upholds the classical approach to music (which it must, to be considered in this category), then why shouldn't it be labelled correctly? Because of instrumentation alone?
If a band is not technically demonstrative then it should be considered didactic, or cultural music, for its other merits and social functions. This would be your Burzums, Immortals, Gravelands, Enslaveds, etc. It is essentially folk music and pre-occupied with tales and ideas and fantasies, and with social cohesion - a shared experience.
Of course this tidies up the approach and changes the line of battle somewhat. It would be fair to praise later Emperor for its technicality then, understanding that - like a study as opposed to a complete opera - it is a work of musical technique and performance training, and not an ideological statement.