I think it would be best to mold our knowledge around the key questions and the myth. This should really be the only starting point, rather than what the eggs mean in Alien, or what the SJ is all about, or what the connection between the two films is.
How is it related to the myth Prometheus?
He stole fire from the Gods to give it as a type of technology to mankind.
Most importantly, what is the fire in this movie? (Try to answer this fundamental question before speculating that Vickers is an alien-cyborg who plans to use SJs to travel back in to time rescue the dinosaurs.)
Scott had said before, that the ship represents a challengeto the gods, and that by crossing that line, very bad things start to happen.
What is this challenge, or how do they cross the line?
Also - the main reason why this expedition takes place is due to Weyland's/Shaw's desire to find the answer of our origin. They are convinced that they left behind maps to come and find them to join them. Why are they wrong? Why are the maps on Earth not an invitation?
One answer is to simply say that there is no fire, that the Aliens/Engineers simply used the planet as a mechanism to stop their creation from getting too advanced (whereby if they were able to travel so far away), and as such send a Juggernaut back to Earth to stop their advancement. This I believe is the most putative response. From here I believe we can add, deduct, and morph the concept based on other things we have heard/seen from trailers, interviews, etc.