Just one point:
I just hate the idea of the shivans being bred, it makes them much less scary, whatever they can do. If they cfan be bred, well... it's the complete opposite of the elemental force, btw (sorry icefire). An elemental force would be born from nature (I don't mean the shivan are the universe hanger and all that bullsh1t, tho). Bred creatures are unatural, you know, genetically enhanced insects, grown up with hormons, hop! I stuck a plasma gun between their shoulders, hop! a super cutting claw, hop, laser eyes! hop, I'm god, I just created a species --> creator is superior to created (since w/o him, the created wpecies wouldn't exist). So shivans= inferiors, so shivans= not scary, even if they can destrooy stars and are billions. It's just the feeling, bred species sux and can't be the bad boys of a story (robots are another story). btw, Aldo, where did you heard the aliens were bred by the other xenos like the one in the Alien1 derelict?