First let me say I do not like the 4-6 man assault unit size. I would prefer a squad of 10-14 over a fire-team of 4-6. But since it has been announced and There is very little chance of them changing it I was trying to think of away to make the aliens scarier despite the "Epic Hero" action style they are making it (Instead of the suspenseful horror/survival style of the old game).
So Since aliens need to kill things to look dangerous, why not add a lot of NPCs and/or NPC bodies to maps.
Then also Add NPC resistance to terror missions, so you enter a map to the screams of local police shooting pistol at aliens and being torn apart? Also this allows terror missions that are traditionally harder to provide some distractions and support to make it more reasonable for a fire-team of 4-6 to take 6-12 aliens (some being the generally more dangerous support units). Even if the police only kill 1 or 2 aliens it gives designers and reason to not have all the aliens in defend-able positions and waiting for you and some distractions so you can get in close and make some early kills. Plus I think Thin men should be able to look like police unless your up close or they shoot at you.
On non-terror missions I always see farm houses with no people and no bodies in the original. Give farmer Joe a shotgun back him in a corner of the barn and put the bodies of his family all around him. Maybe he takes out 1 alien ... maybe not. But again it makes since then for the aliens to not be in the best defense positions waiting for you since they have been busy. There are some times 3 houses on a map 9 aliens are shot down on the property. 2 killed in the crash, 1 already injured in the crash killed by a farmer, and the other 6 dispersed and clearing the area until you land... Now it seems plausible that your 4-6 man fire-team could defeated 6 superior aliens by isolating them and forcing a number advantage on them 1 at a time before they can regroup, position, and use tactics along with their superior firepower and abilities.
In the videos I have seen so far, they have had 4-6 well armed aliens grouped up in a dependable position with no distractions waiting for your 4 guys to attack from an open area starting point... and you win with only 1 casualty or none?
You should lose two guys running to cover the first turn in that scenario because their just waiting to pick you off. They should have had 1 guy on the roof which would have taken out or at least put some resistance to several of the scenarios and you would be looking to take 3-4 aliens with 1-2 guys in close range combat (sucks to be sniper) and 1 alien could be a Muton berserker. ... ya not good odds.
A little bigger map, spread out aliens, and civilian distractions... do able.
Edit: This is actually confirmed in the game , thanks to pjstetson for finding the post. (link fixed 04-30-2012)
Just the relevant quote:
GameSpy: Will there be police officers or other armed civilians in there?
JS: You'll encounter other troops from around the world in the game, for sure.
One would assume they would be on your side. While they did not confirm that directly and I guess aliens could have gotten to them and you could be fighting them, I will say that most likely they will be used as I suggested above.