I think it's pretty much well established that Space Jockys/Enginere's have been around the longest. I think that postulating that they need anything from predators at all limits there status in both universes. Obviously they are genetically superior, and are of a more pristine DNA, and have mastered that sort of engineering.
Crossovers and the like, just because a poor movie is made doesn't mean that the they have nothing to do with each other, or Alien resurrection would have invalidated the entire series. We just have to deal with what we have. The moment James Cameron allowed the Alien skull to be mounted in the trophy room of the predators ship, the two universes came togeather, and when the movie cane out, it was solidified. Obviously the movie version of the Steven and Stephanie perry book prey would have been, a better story. Which goes along with the comic books.
That black liquid in Prometheus is a mechanism for alot of speculation on what could happen, and how things are the way they are. Its more probable that Predators we're early creations of the engineers, or that they are independant completely. There are several similarities between both, Intellegence, size, strength, apparent insignificance of humans, lifespan, space faring. Even if and this is speculation they are just 50,000yrs older than humans, engineers have been around for billions, and Predators have a sorta one track mind everything they do is for the hunt if to improve the hunt. Since clear connections have been made between both series , citing movies and comic books, and Fox owns the rights, I see no reason to refrain from artistic speculation.
Regards
SF