Got news for you folks. Things don't get written in one pass, anywhere, ever. The Wizard of Oz had 12 scripts, rewritten, and 4 different directors. Things get changed on the fly and included/excluded on a whim. I'd be worried if the script for Covenant hadn't been rewritten at least once.
What does that even mean, rewritten? Is that a total-makeover, starting from scratch each time? Is it a minor revision, or a big change? Did they alter the font, from Comic Sans to Times New Roman? It's good to revisit a script and reconsider what you're working with. Movies aren't shot in order and certain scenes are filmed or not, due to various reasons. If I remember correctly, the end of Alien the way Ridley shot it, wasn't in the script, and almost didn't get shot due to budget constraints; he wanted to shoot it in the buff, but that idea got scrapped, and beyond all that, originally the alien was supposed to win, killing Ripley and steering the ship towards Earth using her stolen voice. And supposedly there was another version, never filmed, where Ripley fights the damn thing outside the ship via umbilical cord and kills it by shooting it in the head with a pistol.
And Lambert was originally supposed to crawl into a locker and die of a heart attack, but they didn't have time to film that, or the funds, so they recycled footage from Brett's death scene and recorded Lambert screaming (and it worked a lot better, I think, than the original idea would have).
What I'm worried about, I suppose, is the lack of budget constraints, not the script. Ridley didn't have much to work with and had to get pretty creative in spots, and so of the best scenes in Alien were shot under the pretense of a limited budget and shrinking time table. Granted, the rough material Terry Rawlings had to work with was something like four hours, if I remember correctly from his interview on the DVD's making-off featurette, so they were able to shoot plenty if not build everything they wanted.
The biggest issue of all for Prometheus was the editing. That's it, plain and simple. The damn film is too short, too truncated. Even if the script was stellar, the editing for that film would have ruined it, in the movie's present state. If anything, I would pray to the film gods that Ridley actually edits this one proper.
