Now, I want to say that I know there are economy mods in the works already, but those deal mostly with just prices and possibly item availability. What I mean by a living economy is that the game world actually reacts to economic forces and has dynamic industries that hire on more people or lay them off as different areas become more or less economically prosperous, militarily dangerous, and have larger markets to sell their products to.
This means, at the basic level, adding a large number of more generic NPCs and "labor camps" or "laborer lodges" for them to live in. These extra NPCs will sit "off-map" as potential immigrants or just stay in the streets of cities that are too poor to have jobs for them until they can obtain a job.
Also at the basic level, each town will have its own "Economic Prosperity" rating, which will go up as the town gains more material wealth through trade (which the player can positively directly impact through selling to shops or investment and negatively directly impact through stealing) as well as through the industry of its work force.
Around each town will be an "economic zone" for the town that represents the area that is considered safe for workers to be dispatched out to. These start out fairly close to the cities, but can be expanded as the player clears out dungeons or completes quests around that city. When an area is cleared, its surroundings can become part of the potential economic zone of a city, provided the city can spare at least a couple guards to patrol the area.
Cities also have variable numbers of guards (and track losses of guards), where they focus upon protecting their town first, and then protecting the economic zone around their town second. When they have more than enough guards around their town and current economic zones, they may also try to expand their economic zone by clearing a dungeon themselves.
The economic zones will allow for hunting, woodcutting, farming, mining, and other potential economic activities. Because actually having buildable and destructable housing is a little much to ask from such a mod, it will probably mean that we put in some "miner's lodge" housing next to a mine that just gets locked up whenever the area has not been cleared, and gets unlocked when some laborers move in.
The actual impact of all this would then be that the player could actually see the dynamic impact of their actions upon the game world as they travel and perform actions. Further, the more economically prosperous a town becomes, the more goods will be available in those town's stores. The mod could potentially also remove the leveled lists for merchant inventories, and instead replace that with economic prosperity tables, so that in order to order in a suit of ebony mail, you have to find a particularly prosperous merchant.
Further, depending upon the economic industries available, different types of goods might have wildly different prices. Ebony mines being active might drop the price of ebony equipment and raise their availability, for example, while farms being productive decrease the cost of living, which drives up more general prosperity and reduces the prices of labor. I'll probably have to have a second post to go over the reasons why I don't particularly agree with how most people handle "supply and demand" (they always forget that "demand" part), but this post is for the basics.
If the civil war is still active, the mod could allow Imperial or Stormcloak forces to raid other the towns under the opposing side's land for resources, and to harm the enemy's access to resources. The soldier counts in each side's forces could be related to the relative economic prosperity of either side's holdings. Between advancement of the civil war plotlines, smaller scale skirmishes to reduce enemy troop strengths in the coming battle would become possible, and potentially even mandatory to reduce the difficulty of the attack, especially if your own side has to pay of its own economic prosperity to replace the losses in the field.
Further, monsters, dragons, and other factions may not sit quietly and let you expand in peace - you will have to drive off the wild animals that try to re-take their formerly cleared areas, and this can actually generate procedural quests for the player to fend off the attacking wildlife, lest the wilds reclaim a portion of the economic zone around a city.
The game could also be expanded in that you, as a player, could purchase and own and operate some of these economic ventures. Because the economic factors involved in these systems would not be static, you could have a much more deep and enjoyable experience owning property than to just get a weekly lump-sum 500 gold for your holdings.
So, I'm looking at reactions on this front, and suggestions on how to improve this idea... I actually have three or so other mods I'd rather make before tackling such a major project once the SDK comes out for Skyrim, but I think this is the most far-reaching of ideas that I have, and would like to see people try to pick it apart or come up with things I haven't considered about the idea.


, but that might be that could still happen I guess.