In the mirror universe, wouldn't the Ferengi be communists? I know mirror Brunt is nice, but mirror Nog's whole subplot gives the distinct impression that, in general, the Ferengi are pretty much the same in both universes.
In fact, wouldn't the Klingons be pacifists? The Cardassians anarchists? Now that I think about it, the DS9 mirror universe episodes could have been very interesting if the Terran Empire was still around and Sisko and the gang were traveling back and forth to help the Klingon/Cardassian anarcho-pacifist alliance defend Terok Nor from the bloodthirsty Terrans. Could have been an interesting juxtaposition with the prime universe Dominion War.