Can't resist joining in the fun of speculating/making wish lists about what they'll release. The central theme of my broadcastlust is Steber--I just took a stroll around the ol' database and she was in quite a lot of broadcasts, and I don't think that many of them are things I've seen even on Naxos or Bensar. Otello in '52 with Vinay and Warren? I'd take that. Wozzeck? Lay it on me.
Out of curiosity I'd love to hear Traubel in The Man Without a Country. It's kind of a stand-in fantasy for The King's Henchmen, which was too early for broadcasts. (Don't ask me why the one subs for the other...American operas that fizzled but featured a big star, I guess. King's Henchmen had Tibbett, and a libretto by Millay, by the way.)
There's some Thill including a partial Faust with Rethberg, and a Boris G that's probably not in Russian despite the presence of Kipnis--it's 1943 after all. And that one has Thorborg.
And of course there are some things with pet singers of mine, El Amor Brujo among other things with Jean Madeira, at least a couple of 'casts with John Alexander (unless it's another Alexander)and so on and so forth.
Met Maniac's Lost Broadcasts page features some partially extant broadcasts that are the stuff of dreams, some largely irretrievable Leider and Melchoir, zum Beispiel.