Prometheus: A Rethink

First of all, if you have not yet seen the film I suggest avoiding this thread. Second of all I have not seen the film, yet, and unfortunately will be unable to watch it in the immediate future (personal circumstances) but I will watch it in due course. Therefore my theories below are based off comments from those that have already seen the film - I asked them for the information, as spoilers do not bother me. [u]Engineers[/u] At the beginning of the film we see an Engineer sacrifice himself, his DNA seeding life upon the Earth. From the footage I have seen in the trailers there seems to be a key difference between this Engineer and the Engineer seen later in the film - appearance. The Sacrifical Engineer appears "biological" whereas the "Last Engineer" appears "bio-mechanical". [u]Humans Fate[/u] I have been informed that the Engineers had targeted Earth 2000 years ago, but for reasons not clear waited until the crew of the Prometheus arrived on LV-223 before launching their attack. [u]The Xenomorph[/u] According to the information I have been told the Last Engineer ultimately gives birth to an Adult Xenomorph after being impregnated by "Cuddles" (tentacle monster), whom ultimately is sourced from the ampules stored within the temples. [u]My Theory[/u] Here goes... The Engineers are exactly that, Engineers. Originally they were biological engineers that sought to seed life throughout the universe, and assist in the development of said life, as they once did on Earth. For intelligent life to evolve a planets ecosystem needs to be systematically "shook up" by near-extinction events, causing the surviving lifeforms to adapt and evolve to a changed ecosystem. Thus the Engineers engineered the perfect organism as a means to artifically create such near-extinction events. Now 2000+ years ago, either through choice, force, or after the "force-landing" on LV-426, the Engineers, possibly having reached their peak in terms of evolution became a bio-mechanical race. Adding to their genome with mechanical elements, allowing them to develop beyond the limitations set by nature. As they "upgraded", they realized that bio-mechanical life was more efficient and more controllable that biological life, and thus there outlook, their goal changed. Rather than seed organic life on planets created by nature, they could create bio-mechanical life on planets they had created, powered by stars that would never die. Thus their plans changed. All biological life they had created was to be deleted (using the Xenomorph) and replaced with bio-mechanical life. Now to LV-223... The Engineers stationed on this outpost, because of one of their own falling victim to its cargo (LV-426), were tasked with re-creating, re-designing the Xenomorph to ensure it could be safely transported. These engineers, used urns, ampules to store and transport the creature, but when adding to the creatures propagation with a new progenitor breed (Cuddles) they fell victim, once again to their creation. I would greatly appreciate opinions and views from those that have seen the films.