Zombies should never be a ranged opponent. When more NPCs are in, I don't think this will be an issue, since you'll naturally have raiders, cannibals, rapists, ex-politicians and so on. I also think thats not a simple addition.
What might be cool though.... I've never seen a river turn into a lake in game. We have tons of lakes in the NE. Heck, go a couple hundred miles east and you'll hit an ocean. Might be a nice option to be able to turn on lakes in mapgen. Or even have an option where the map is normal north/south, but turns to desert in the loooooooooooong west, and ends in ocean in the east. Dunno, I guess its stupid, but some overall stuff like that would be cool.
At the very least, for a game set where I live, water should be more of a fact of life. You can't walk a mile around here without hitting a stream. I can't imagine dying for lack of thirst. You'd have to be a moron - and lakes are just -everywhere-. Lakes, boats, and so on - they really should be more present as a geographical feature, even if you don't deal with the whole ocean thing.
I mean, heck, even if you ignore all the waterways around here...just look at the old coal mines. You'll get more subsidence due to those then you'd -ever- get in a wetland, simply because you have whole areas underneath entire cities peppered with 2-4 hundred year old coal mines. They subside enough now (you hear about it on occasion) - I can just imagine what they'd be like after the sewers let out and flooding set in. Plenty of old flooded mines dot the area already. Supposedly there's usually good fishing in them, but I wouldn't know, you wouldn't catch me dead doing something as stupid as that.
I guess I'm just saying that some more northeastern features in general would be nice, as the area feels more 'generic suburban/suburban-rural US' right now.