If hewasn't Ennis, Jack wouldn't love him. There've been several fanfictions written about the two of them living togetehr, and in all of them, Ennis changes, perhaps s little too much. But for Ennis to agree to live with Jack t begin with, there woukld have to be a huge change, so--there you have it.
Unfortunately, it'sd Jack's death, and the discoverfy of the shirts that changers Ennis the most. And I think, if Ennis is ever going to be happy, it will probably be much later with someone else (as in the enormous and enormoiusly rewarding Ennis" (revently posted on fanrfiction), or even my tiny "Be Nice, Wouldn't It?").
The paradoxicakl tragedy of BBM is that Ennis wakes up to the fact that he has lost the love of his life--after he has lost the love of his life.