I love a good take-over-the-world game. On the dev page, it looks like Toady is already gearing up for more army and foreign entanglement features. As these are developed, it might be interesting to see Dwarf Fortress provide an Empire Mode to complement Fortress and Adventure Modes.
In Empire Mode, you would be managing a nation rather than a single fortress. You could try to raise an army and take over the world (I would) or simply fortify yourself against circumstance and try to run your country as long as possible. This could be a very fun new way to enjoy the existing fantasy world simulation.
Empire Mode would be more zoomed out than Fortress Mode. Time should move faster, allowing you to play through several generations of emperors. The various settlements under your leadership would be mostly autonomous, but you'd have the ability to order specific items from them, based on their natural resources and population. For example, if the fortress Clamblight has magnetite and Roadfleck has marble and Orbflags has a legendary weaponsmith, you could order Clamblight and Roadfleck to prioritize mining magnetite and marble, ship those resources to Orbflags and then order Orbflags to produce steel weapons. For there, you would send your armies to Orbflags to pick up steel weapons, or have Orbflags ship its steel weapons to fortresses in need of defense or fortresses where your armies are already stationed. You might be able to zoom in on a particular fortress under you control either to take command of an industry to control your troops to break a siege or destroy a forgotten beast.
You gain new fortresses by sending expeditions to build new colonies as you would in Fortress Mode, or by annexing existing fortresses. There should be ways to annex fortresses other than force, such as by trading land or resources like the Louisiana Purchase, mergers like Scotland and England to become the United Kingdom, political marriage or political intrigue, like assassinating a ruler and installing your own puppet government. There could be varying levels of annexation, for example think about Florida, Puerto Rico and Mexico. Florida is completely annexed by the USA, Puerto Rico is partially annexed by the USA, Mexico is not annexed but very friendly to the USA. Non-annexed entities can engage in trade, with the player setting prices and trade priorities for each fortress. I'm thinking that the player can use this to try and monopolize certain resources and use high tariffs to economically conquer or control other entities.
As in the real world, it should be difficult for a nation to stay in one piece for a long period of time. There should be factors that allow annexed fortresses to try to secede or for your government or dynasty to collapse. The thing about take-over-the-world games is that they are designed with a winning condition, and Dwarf Fortress should not have one. Keeping an empire running should be a constant struggle, just like keeping a fortress running.