Okay. Here's a thought. It's probably not a new thought at all, but...it exists.
No one can die. Unless they're burned. I'm going to go with burning actually working for now, until proven otherwise. If I missed a line of dialogue somewhere that contradicts this, let me know.
So. Let's say Jack was incinerated. Instantly. Completely. How does he come back from that? I mean, of course, prior to the Miracle. And I know he's been exploded and came back from that, but burnt to nothing but ash? That isn't regenerating cells, as there is no point to start from. Just...ash.
Also, if Owen had really wanted to die...couldn't they have incinerated him? It'd work the same way, I imagine.
I'm going to go...stop being morbid now.