Quite honestly, I would not be surprised if this forum had this idea already but seeing as Im new to the site, Im not digging through an unknown past.
The Idea is simple: Allow players to LAN their world together via a server and pick fortresses in different parts of the map (or in the same if on Adventure or whatnot).
This would allow others to interact with both NPC fortresses and players or even declare war on them. Leave any chat function up to IRC or some other chat medium (like Skype or Mumble).
What we would need: A server set up that runs like any Dwarf Fortress world. Generation same, time placement and all that the same but just has to watch the placement of several fortresses. Also has to be able to read the data that a player creates using their own fortress. I understand that this game can kill even the most die hard of computers in the "end game" but the Server just manages the info and relays it to other players (when they would go into a world map-esque thing) while the player's box still deals with all of the items on their end.
Why would we want this? Because I have played DF for a while (still run on DF df_28_181_40c) and while I love the game, I would love to see another player's trade caravan come into my market and offload goods that they made. Might also increase the time before the merchants leave (seeing as sometimes you lose the chance when your dwarves are running a large amount of supplies and your trader doesnt do his job).
Like I said, wouldnt surprise me if this has been suggested already but nevertheless I like the idea.
-NK