Okay, well this at least explains what happened to Ai-Kun. Perhaps Ai-Kun is meant to be the bridge that helps us understand what the Vajra are all about? On the one hand, Grace says all they're about is "they're in our way," and on the other hand she calls "the planet where the Vajra's true queen resides" her "treasure island."
So now I get what was so special about Sheryl and Ranka's singing, specifically-- their voices produce fold waves, which are somehow in tune with the Vajra. But what's it all for?
And so the Macross Quarter goes rogue, and Alto and Ozma wind up on opposite sides. Can you imagine that ever happening to Rick and Roy?!? Well, I guess Rick may have been thick, but he wasn't quite as obstinate as Alto is, and I can totally understand Ozma's thinking on not including him.
Only three more to go...