The atmosphere, character development, etc., are doable, but what to show in place of the "will they survive?" storyline? The answer refers to "does humanity deserve to survive"? Does that imply drama, with human beings in conflict with each other and the alien used as a tool in that conflict?
Reminds me of the unused script for the third alien movie, with groups of human beings fighting over the alien, fighting against the alien, and fighting with each other.