I had three players. Here are the characters they played:
Player A: Miller
Player B: Rye (actually Lucas)
Player C: Wilson -> Clayton -> Flynn -> Johns -> end of scenario
Player C's characters died a lot! All four of them actually, but he took them over in situations that were very lethal.
With the starting set of characters, I didn't want to make Wilson play Lucas, because he already has his own agenda. I liked the idea of captain Miller honestly being in charge, so I gave Lucas to Rye. It fun to have Miller attempt to make things work surrounded by two characters with very different agendas. I also didn't want Lucas for myself, because for me it's a lot more fun to see what the players do with the characters.
Lucas' act 3 agenda says "You must stop Weyland-Yutani from getting an alien specimen back to Earth at any cost". You could focus on the "back to Earth" part, but my player instead focused on the "Weyland-Yutani" part and decided to bring the whole ship to Bionational instead. If the goal was the destruction of all alien material it would make sense to blow up the ship or fly it into the sun, but we really liked the idea of this lone android flying a ship full of aliens back to humanity. It would make for a great sequel!
Again, this is not the one true way to play the scenario, just what we did.