Thing is he was just making a refernce to the Bible(or christianity whichever you prefer) and really that isn't an uncommon practice. Good example would be the Puritains who form what I learned tried to associate everything with the bible as much as possible, so what Ibosquet did shouldn't be shot down immediately(if you didn't mean it that way sorry, to me it kinda sounded like it). If anything I think this is very interesting, who knows this might have actually been the pattern the manga-ka was taking.

I myself am not religious and don't follow any religion whatsoever,don't know what to call that. I'm pretty stupid so not even gonna bother trying to figure out a lot of religious stuff, but what little I have heard of religious preachings and such I can work my puny little mind to find my own interpetation so only take anything I say as that when it comes to such matters.

As for heaven and hell, well one would think heaven would be filled with whatever makes one happy and hell would be filled with whatever hurts someone. Though I think Gantz more of like a limbo as they are dead but alive at the same time.(they wonder the earth trying to get the right to live) Not exactly like limbo but meh I guess the point is across.