Also i dont think we need to do a movie about the Space Jockey, you see from Alien here is what we got...
1) A Horseshoe Space Craft, Crash Landed, with a Dead Skeletal looking remains of its Pilot with a hole in his chest area.
They spot a burnt hole in the floor next to the chair, one member of the crew gets down to the lower chamber and we see a Cargo Hold of Eggs.
From Alien to Aliens etc we find out what these Eggs contain, and so we can assume one of these Face Hugers got to the Pilot at some stage.
It would appear that this would have occurred at some point during flight. And the Pilot let of a Warning SOS.
PROMETHEUS
Shows us same kind of Ship and confirms they are used as Bio Warfare Cargo Ships.
We are shown the Space Jockey could be a Engineer in a Bio Mechanical Space Suit (yes there is size difference). But the drafts had them to be same size as Space Jockey from Alien.
These clues then add to Alien that indeed the Space Jockey may had at some point got Face Hugged while he had his Mask off Maybe? Maybe most likely when he inspected the Cargo Hold after a containment warning went off, or he could have been wondering around unaware that one of the Cargo had got lose.
This scene or similar is the only thing that could be added to explain what happened, by the actual events but its not enough to base a movie on...
Ridley has also explained off film what happened and that indeed the Space Jockey/Derelict and Engineers/Juggernaught are all related to each other.
The Space Jockey was a Space Suit, and the Derelict was transporting a Cargo of Eggs, when the Cargo had got compremised and one of them got to the Space Jockey..
Knowing his Cargo and himself had been compromised and knowing his fate, the Space Jockey set course for the nearest baron moon he could Quarantine the Cargo.... but during the final stages of this the ship Crash Landed, maybe either during being Chest Busted or just as this was about to happen....
At some point a SOS Warning was set off, be that automated, or set by the pilot before or just after the crash.
So we know what happened, only thing we could add is show the Derelict being loaded with its Cargo or show how it got onto the Derelict.
Show the Space Jockey get face hugged i.e where was he and how did it happen, show him then get back into his seat and set a course to LV 426 and activate the SOS... Then show the Crash and finally the Chest Buster Scene.
But is that necessary, does it show us what we do not all ready know?
R.I.P Sox 01/01/2006 - 11/10/2017