Ha, definitely agree with LPS' second point.
Other than that, as I mentioned in my first post, I think artistic freedom such as in the books is what you need to turn a "run from A to B and shoot things" plot into something bigger, Alien isn't really any different either if you come to think about it if you remove people.
So, why not add people to the plot? Movies with just one person, one protagonist can be successful (see Die Hard) but on the other side, the Unreal concept would flop this way, it could feel like an "endless" journey which bores the watchers to death.
Moreover, experimenting and adding more
living people could allow for some "funny" eastereggs which the players would understand but which would add a lot of depth and maybe surprise the watcher who doesn't know the game.
Imagine the following scene: In the Vortex Rikers, 849 just wakes up from the crash after the introduction showing the spaceship crashing on the planet's surface, leaves the cell, explosions here and there, cables dropping, metal bending noises and earthquakes - suddenly another closer explosion. He looks to his side to see another person leave her cell in shock when all of the sudden the hallway above her breaks and crushes her just in the moment he started to talk to her to ask her what happened.
(Those who never triggered this event on purpose when playing coop to kill your friend shall throw the first stone!

)
Let's take this a bit further and make 849 actually form a group of survivours with him as the leader inside the ship. There you got the interactions, tell some stories about the other people (excluding 849, this can be solved the easy way by interrupting him everytime he starts talking with a Skaarj, Brute, Manta or Krall attack or some other sudden event), the stories could show how the "normal life" in the Unreal Universe looks like, how the judgement system works like and if it is corrupt, what the others did to be sent to the prison moon and slowly decimate the people until the "Kira part" of the plot starts to add more focus on that or keep some alive and give Kira some important role, maybe 849 searched for some spaceships on board of the Kran but he didn't find any because certain doors had a safety lock? That's why she might be an interesting plot part.
You see, the key to make it more interesting is some artistic freedom.
And I would say the action should settled in the story of Unreal 1. Why? Because I think Na Pali's environments can be updated/turned into a beautiful scenery, see LPS' remake. They could still expand it with stuff like a Krall rebellion or something like that to give it more depth and let the movie series end with a cliffhanger indicating that there will be the Human-Skaarj-War.
However, as we all know the movie industry, I think we all know that they would just create an epic fail, either something that doesn't resemble Unreal at all except for the name (2nd point of LPS' post) or they would keep it too direct and mess it up by making it a boring experience.
And to keep it realistic, I doubt Epic would give anybody the right to make such a movie, no matter how good the person is at doing that, they would probably do a Gears Of War movie, but Unreal has a down at the moment.