I have been thinking about your subversion concept, tpe, and here is what I think.
In a sense, Jack and Ennis are the ying and yang of the cowboy stereotype: Jack, the rodeo cowboy who thrives in the limelight, who is the life of the party, the best salesman, and Ennis, the quiet devoted hard working solitary figure who knows what to do and how to do all things around the ranch, fixing the engine, pitching the tent, shooting the elk, cooking and protecting the sheep. That's what makes them perfect together, not competing with each other, but respectful of the other.
To me, Brokeback Mountain and Jack are definitely subversive of the iconic cowboy, but Ennis was the iconic cowboy that was subverted. He was the solitary figure content with nothing and beans. Jack was the rodeo cowboy more interested in belt buckles than doing the work around the camp. Jack was the one who wanted more than a few high attitude f@#$ks a few times a year. Jack was the one whose love kept their relationship going for twenty years. As far as Ennis was concerned, they could have left it on Brokeback that summer, and he would've been just fine with Alma and the girls...not passionately happy pawing the white from the moon, perhaps, but fine nonetheless. It was because of Jack, that he was like that, with nothing, a nobody without him, brooding in the bar alone, drinking beer after beer, like any iconic cowboy would. That's what the short story led to, the lonely Ennis living in an empty run down trailer.
I think it was Heath's genius to transform that miserable figure from the short story to the radiant symbol of an iconic cowboy made human, extending the strength and silence to embrace the frailty and sentiments of a man capable of love. So the answer to my earlier question, whether fear of love is innate to the iconic cowboy, is affirmative, but Heath's genius changed that, and made it possible to be a solitary self-reliant cowboy, with feelings. That's why Brokeback Mountain resonates with so many, and why Heath deserved an Academy Award for his performance. It was ground-breaking not because of the gay issue, but because of the fundamental American mystique of the cowboy and love. The fearlessness of Heath drove out the fear of love in the cowboy.
Heath turned a subverted cowboy into a new hero, for me.