The doctors Ray M and Greg Z said in an interview many years ago (and I'll try see if I can find a link or maybe other will help with this as well?) that the story dealt with artificial intelligence, and it is a cautionary tale of how (dangerous) artificial intelligence can go wrong. As I remember it, mankind invented these reapers to help us with something? (sorry, been a long time since I've been following Mass Effect).
I also think it is simply about being human, what is it to be human and how humans will behave when they meet other species that are not human e.g. how do Shepard behave when meeting - yes - aliens. Is he cordial to people he meet or is he a renegade? I agree with almost everything that has been said about the meaning or interpretation of the game.
And yes, the hero reborn can, I think, in fact, be traced back to the old egyptians. Here's one from Egypt, involving a coffin:
http://en.wikipedia....Osiris_and_Isis This just means that the ME3 writers do indeed know their classicals texts, probably becuse a lot of them are English Majors, maybe...
As a sidenote, Dragon Age does something similar; the mad mage (or scientist) in Watcher's Keep, experiments with -ahem- something or someone, in Golems of Amgerrak you see (some of) the results, and the dwarves sort of do the same with their use of and making of Golems.
And to continue a bit, isn't Commander Shepard a Golem now? Does he not have cybernetic parts in him now? And can he then still be considered human?
The reason why I bring up that Ray and Greg are medical doctors is exactly because of this; their first software was to be used to help doctors decide what actually was wrong with patiens. They called it - BioWare - and so the company was born. I've always wondered how much impact this had on the stories, they really wanted to tell. It seems as with the Mass Effect series, we might have gotten an answer - at least partially.