Not a prequel, not LV426

Although I'm pretty sure this has been said, or assumed already months/years ago, what about the theory that the ship in "Prometheus" is simply ANOTHER "Space Jockey" ship and NOT the one that crash landed on LV426? I'm assuming that the movie is set AFTER the events of the original "Alien," and much farther in the future. OR It could be a sideways prequel, with the events happening BEFORE the original "Alien" yet unrelated directly: different Alien ship, different planet. After all, the trailer alludes that there were more than just one Alien ship roaming the cosmos. I also am thinking the "Space Jockey" race is a xenomorph race similar to the "Genestealer" race in Warhammer 40k lore. The "Space Jockey" race absorbs a host to grow in and on, and takes on and steals some of the genetic material of the host race. Pretty sure that the Alien xenomorph race and the Space Jockey race are the SAME race.