So what are the chances...

I'm thinking that the Space Jockeys might actually be some type of genetically-enhanced super humanoid, like a soldier perhaps. I mention this due to a sketch I saw online where the Space Jockeys are shown with weapons in hand. But, to your point, I think the Engineers can somehow since that the intentions of people such as Vickers(and David, maybe) are sinister and send their creations to prevent such theft.

Mind you this is just a notion, pure speculation. Looking at the planet from all the photographs, it' s scorched, barren, lifeless. Even with atmospheric moisture I don't see any plants amidst all that topography. If this planet was a research outpost with specimens from many of the various project worlds the Engineers had propogated, they may have continued their research with live specimens there. The often mentioned pile of bodies/suits including the head does not bode well for these researchers. Even the exterior of their complex is erroded, and crumbling. Yes I'm aware that eons of time can duplicate these effects. I'm just wondering if something happened there between the test subjects, and the engineers that resulted in a single individual, be he test subject, or engineer entombing himself in stasis. As there is nothing left on that planet at the time of Prometheus's arrival, why not go to the origin world of these intruders, invaders. They have a limited defensive capability, a viable biosphere, and perhaps compatible genetic material. Much like Weyland looking for immortality, it presents an opportunity to pick up where you left off so long ago.

ummmmmm no. Your wrong.