This is meant to play in with the recent development of multiplayer, via Carnes' amazing system. It assumes you know how to connect to that and how to use it. If you do not, find the appropriate thread(s) on how to use it.
The Challenge: Miniforts.
The Premise: Individual, self-contained forts in a single embark.
The Tool: Dwarf Fortress: Multiplayer Edition.
The Specifics:
Due to the complexity of designing a single fort, and then multiplying that be the number of players, it's highly suggested to keep the number of participants low, or else spend a lot of time waiting for everyone to finish doing their stuff. 6 players should be considered the rational maximum, perhaps encouraging people to share forts?
Each starting player gets one of the starting 7 dwarves. It helps to boost the embark points very high. Each starter dwarf gets a pick, axe, anvil, and some supplies. If the number of players is low enough, allow them to double up on dwarves, at player's decision. Supplies should be distributed as fairly as rationally possible. Seeds are difficult to share, due to the way they appear in the same bag, so a preference to give plants to dwarves is preferred, and consume the plant to produce seeds. Utilize the caravan traders to acquire difficult seeds, and just kinda free-hand it when giving seeds to players. It's not going to be an exact science with seeds, and the specifics will be even worse.
Reserve at least 1 dwarf of the starting 7 to be the Community Leader. The Communal Fort is a central location where caravan trades are performed, goblinite is stored, and emergency resources produced. This should ideally be a very small, enclosed community, minimal dwarves doing very little. Include the manager/broker/bookkeeper here, as well as militia commander. The communal fort shouldn't be used much, but should be where any non-explicit supplies are stored, such as pillaged goblin weapons. for simplicity's sake, trade should occur here as well, and be distributed to the forts as needed.
In order to keep possible contamination down, forts should have as close to zero contact as possible. Trade should occur via airlock doors and special dump/stockpile usage. Trade with the communal fort can be a bit less strict, as the communal fort should never die. If they make friends with a cumminity member, it shouldn't matter because that friend will never die and trigger a tantrum. Otherwise, trade and cooperation between forts is allowed, though discouraged. Backstabbing and lying is allowed, and encouraged.
Military is a shared zone. Each fort is responsible for their own survival, and it's their choice to wall up or send military out. Trading for armor/weapons, or trading for protection could be vital here. Backstabbing should also be vital, by encouraging someone to move their forces out, and then withdrawing their support and letting their fortress suffer. The ideal "winner" is the last fortress or fortress alliance left standing. Any goblin drops are considered community property, unless explicitely said. If one player makes an effort to send their forces out while the other players keep their fortress walled in, then obviously that player should receive the profits of their effort. If the goblins attack one fort and are killed by traps, then that player got lucky and gets the loot. If the goblins loiter and 3+ forts go to kill them, then it's community property, unless 2 of the players decide to give it to the 3rd. A large amount of "play it by ear" is expected here.
Trade is up to player discretion. If one player wants to gift some seeds to another, that's fine. If one player wants to trade steel battle axes for dog tallow, that's fine as well. Use of caravans is generally discouraged due to the unfair nature, but allowed. The players can decide who gets dibs on what they get from the caravan first. The only rule is that they must use their own fort's produced goods to buy the items. Use of tunnels stockpiles, and closing doors can help ensure that the correct goods are selected for trade. The players can vote on who gets to trade first. Clearly, one player shouldn't be able to buy all the steel bars every year, so some amount of sharing and taking turns is required.
Trading to the community fort, in order to buy goblinite... is fuzzy. It's unclear how to handle this odd occurance, but creative use of coins may be required. It's also possible to make a "neutral fort" of the community fort, an actual player who doesn't participate with others, except to trade goblinite at times, thus allowing this player to decide if a stolen -Iron Halberd- is worth a stack of *Stone Crafts* or not.
Migrants are given to the different forts roundly. First player gets the 1st one, second player gets the second one, third player gets the third one, first player gets the fourth one, second player gets the fifth one, etc... The list carries over year to year, unless dwarves are required for the community fort, in which case the first ones are skimmed off the migrant wave and assigned to the community. This way, no one calls dibs on the migrant armorsmith and no one gets stuck with a migrant cheesemaker.
As for actual implimentation, burrows are required. Every owned dwarf is put into a burrow encompassing an area to be decided. General agreements are that 20x20 is sufficient size for a minifort, but number of players and available land play a roll as well. Consider embarking with a lot of special-colored stone, so that you can mark your territory border early. Due to the way that burrows work, there should ne no unintentional contamination across forts. Forts can be as close to or far from a neighboring fort as desired. Some closeness may be preferred, to give a real community feeling and encourage trade, or be far away and avoid the fallout when forts start exploding.
Intentional cross-fort sabotage is strictly forbidden. It is illegal to intentionally flood everyone except yourself with magma, or to intentionally block off/drain a river to hurt someone else. For the same reason, letting dwarves idle near each other is highly discouraged, as friends cause tantrums.
Also: Prepare for moods. They will destroy you.