How can a search and rescue ship catch up from being so far away versus the cost and time it would take? A second ship was secretly manufactured alongside the Prometheus and has been ghosting it's steps since the mission began. Just a few steps behind. It doesn't even have to be a Weyland Industries ship. Enter Yutani. It looks as a good way to do things since the destination of Prometheus ship was supposed to be undisclosed and no one on Earth should know where they were headed to (Lv-223).
Just hope this Yutani ship discovers that David and Shaw are going to Paradise, and they can follow the speed of the Juggernaut...
If you take the ad campaign for Prometheus as Canon (or at least as some insight into the back story) Yutani appeared to have either worked with Weyland Industries in the selection process of the crew or hacked into their files and watched 'eyes only' material regarding the mission. It was one or the other. I don't recall where the general conscious left it.
Good point about the hypothetical ship being able to catch up to (or at least be able to trace) the juggernaut.
Dealing with the Deacon and any other abnormalities that came from the 'disruption' on LV-223 would be a nice first act.
On the subject of returning actors. Obviously everyone on board the Prometheus was reduced to very small ashes. The only actors who could conceivably return (albeit possibly ridiculously) would be Theron and Pierce. Vickers could have survived just as easily as Shaw did if they wanted her to.
Vickers scratching a living on the surface of LV-223 would probably be better suited for a fan film. Cat and Mousing the Deacon. Trying to find a way back onto the lifeboat. Salvaging useful scrap from the collision. Like Cast Away but with Aliens.
Weyland could return as an android I suppose. It wouldn't be out of character for Weyland to have made a robot in his image. As to how it would fit and be relevant in a new story is beyond me however.