I think a fundamental mistake in assuming that butch/femme queer relationships are trying to mimic heterosexuality lies within the very fact that people in those relationships are in queer relationships. For example, if two female-bodied, female-identified women are in a relationship, it can be understood as a lesbian or queer relationship. The gender performance of these two women does not negate that, even if one dresses in a "masculine" manner and one dresses in a "feminine" manner. It is not that the "butch" woman is trying to be a man; she is just dressing in a way that make sense for her. Nor is she trying to perpetuate the idea that she is in a heterosexual(ish) relationship with another woman: they are in a lesbian/queer relationship. If anything, the play on heterosexuality is just that: play. It's showing off and even making fun, saying "look, we're just like you except we're both the same gender!"
Similarly, when we look at Armand and Albert, it is obvious that they are in a homosexual relationship, even though Albert dresses and acts in a "feminine" manner. They make no attempts to blend in, to act "normal", or to pass as heterosexual in their day-to-day lives. The idea is so absurd to the two characters that it is what the whole movie is based around! "Can these two homosexual men play it straight?" I believe that The Birdcage is a positive representation of queerness because it's such a playful look at homosexuality and heterosexuality as well at hetero- and homonormativity and gender/gender perfomativity. What does it mean to be a "stereotypical gay couple" as opposed to a "stereotypical straight couple"? And what happens if we mix that up and then play with gender a little? The fun really begins when the conservative father finds himself enamored with Albert- who is in drag as a house wife! It rarely gets more queer than The Birdcage.