Wow! That's such a concise way of stating this in a nutshell. I think this might be spot on Lee! Everything about a scenario like that really does seem Shakespearean as far as tragic construction goes... and it fits in with their star-crossed/ moon-crossed status.
Agreed. As dramatic structure, that would make the most sense. And that's basically the foundation of why I prefer the "Lureen was telling the truth" interpretation.
When it comes to how Jack died, I think people probably prefer to think that Ennis' imaginary version was right. Horrible as a hate murder would be, it is actually more comforting in the terms of the story. If Ennis was right, his fears all along were well-founded, and he and Jack would have been in danger had they lived the sweet life. Which would mean Ennis hadn't screwed up his own life (due to internalized homophobia), which is an even sadder fate. And yet, it's one that no doubt befell countless people throughout history.
So as great literature, with its big themes and Shakespearean tragedies and all of that, BBM works better if Jack died in a random mishap.