Just a thought...
Since EMI's all-star, all-studio Tristan und Isolde was suitably well-received, perhaps they can go out with Götterdämmerung instead.
I am listening to Domingo's Scenes from the Ring disc, and "Brünnhilde, heilige Braut!" His voice, given enough time to get the best take and with enough studio trickery, could definitely handle the older Siegfried. He'll never tackle the role on stage at this point, but I think that a studio Götterdämmerung would be dandy.
I mention this to highlight the fact that there isn't really one on disc with a modern (-ish) super tenor. Levine had Reiner Goldberg. Need I say more?