I remember seeing an Alekhine game with five or six queens on the board between the two sides. Was it against Marshall perhaps? Or Mieses? Help me out here, Batgirl.
There can be only one queen

The purported game was Alekhine vs. Grigoriev 1915 but most sources hold that it is a fake. I believe that the game was real but the 5 queens position would only take place "in the notes" so to speak.
P.S. batgirl was luxuriating in a bat-bubble bath and would not be disturbed.

Seems silly to appeal to the pieces as representations of actual battle-objects, since obviously in the real world a queen would be no more powerful than the king.

I'm serious. It's like having two kings, how absurd would that be. Someone should change the rules so that you can only retrieve what has been lost.
The Spartans traditionally had two Kings at once. The Romans traditionally had two Consuls. Many civilizations had polygamy, and thus multiple Queens at the same time.



Having multiple queens is one of the least implausible


If there were to be more than one queen, really what difference would it make to your experience? You don't have to play this version of the game nor do I expect you to, but a little chaos could be fun for those who are just starting out and want to try new things. Strategy is still something that you can use whilst playing although some people would rather just throw that out the window and just have fun. Take that into consideration.
If we were only allowed to promote to pieces captured by the opponent, then the wacky Lasker Trap wouldn't exist. And that makes me sad. :(