All things considered it might be better never to depict the SJs in the flesh in ALIEN(S) canonuity.
Some unknowns are best left unknowns sometimes. Some mysteries best left mysteries.
Agreed. The Space Jockey was just a random passerby. While he is an indicator that the universe of Alien has had at least one other tool-using species out there somewhere and somewhen, his story is incedental other than being yet another victim of our acid-bloodied friends.