They could've done a Newt thing as a DLC for A:CM I reckon, involving the woman colonist the marines find.
Great idea! Why didn't I think of that... You could have multiple outcomes, if you get caught by the aliens, you get cocooned; or survive long enough until the marines arrive, and Newt wouldn't be the only survivor.
...on the other hand, if the SDK was released, I wouldn't just be thinking it, I would be actively working on it.
Mind you. Newt based stealth game would still work as a full game. Open world environment of the colony, different areas to unlock as you progress, aliens always trying to get at you. Day/night cycling affects number and types of xenos roaming around. Food scarcity, hunger, and sleep game mechanics would be needed.
I'm thinking of atmosphere, tension, story, vulnerability and survival as player achievement necessary to progress the game. Obviously, 'PEW PEW! PEW!' game play has been done to death with the franchise. It's time we had a real horror show, throw the girl into peril, I say; and you share her experience!
What's so dull about that?