I don't really see the point of using audio from the characters talking, considering it's pretty much all just what they say in the movie. But Isolation does have some pretty great sound effects. Especially the creature roaring etc.

One other thing. There's a shot near the end where the alien looks at Jonsey's cat box, but in the Director's cut the alien whacks it over. It's kinda silly, but there are two really good reasons you should use have the alien hitting the cat box.

1. In the theatrical cut the audio cuts out really really awkwardly without the cat box scene. Having it fixes this. For this reason I believe, and this is just speculation, it to be one of the "11 minute cuts".

2. It fixes the continuity error of Jonsey's cat box being in a different position when Ripley returns after failing to stop the self destruct sequence.

I also think you should include Lambert slapping Ripley in the face during the scene where Ash and Dallas attempt to get the facehugger off of Kane. You can do whatever you want, but I just really like that scene. It's really short, so it doesn't mess with the pacing, and it adds more tension to the crew and stuff.