Not silly at all. What would be even cooler is if NPC behavior changed depending on the weather as well, via StoryBricks. Although that might be being a little too hopeful.
yeah. I mean, I've talked about it before. I fucking LOVE the idea of a sim mmo. True npc interaction. weather, etc you name it.
I was so excited in wow beta, 20min into playing, running up to Dun Morogh, and you see these snow leopards. And the Leopards will attack the "critters" in the area. Rabbits. As well as players, and Dwarf npcs. (cant remember if they are hostile to the boars in the area as well). They also, avoided the road, but if they did get too close to the road, the patrolling Guards would attack the Leopards. This was unfortunately, basically the most complex npc interaction in the game. Go to Elwynn, and the spiders do not attack the murlocs, nor kobolds, despite the doodads of kobalds in the spiders cocoons.
Predators should behave like predators. Social packs, lone hunters, or what have you. Spiders should attack everything that enter their "web". Cats, should follow npcs, and attack ones that are smaller then they are..
The problem here is where is the GAME in all this. And how does throwing in 2000 players into the mix change the ecology? Players invariably strip mine, and/or cause mass extinctions. and as for the game. Minecraft, dwarf fortress, simearth, etc, are not exactly conclusive to raids.
Generally when I talk about things like this in a game, I separate this into a totally different format. More like UO. focus on merchants, crafting, etc. Particularly with advances ala minecraft, DF, etc.