I think you need to, to a degree (seeing as how the A Deck set was completely self contained with the only access to the rest of the ship via ladder and no sleeping quarters or bathrooms). And there's plenty of scope to add to what we see in the film. I get stroppy when they change stuff from the film - like they did with the Sulaco and colony in A:CM, with no apparent reasoning behind it. I kinda get them changing the Nostromo for A:CM, because the tight corridors probably wouldn't suit a multiplayer game. Changes for A:I seem less necessary.