Army arc; my main interest is in the increased integration of dwarf and adventure mode, so that things that take place during worldgen can keep going (with player participation) afterwards. I'm looking for scenarios like:
* In adventurer mode, you attack a neighboring settlement with which my civ has initially peaceful relations. After a sufficient amount of carnage (perhaps by multiple successive characters from the same home civ), a state of war arises.
* In a state of war, you can participate in the conquest of our enemies and the annexation of their territory.
Along with these, I'm hoping for smoother transitions between Adventurer and Dwarf mode (e.g. being able to leave your fortress alone for a while to go adventuring, without abandoning it). I think that missing element would enable a lot of richer story possibilities. Creating a fortress and being able to visit it as more than a ghost town would mean a massively more interesting connection between the two modes. This could grow into things like armies fighting back and forth over a piece of real estate, and benefitting from it while they hold it.
And just to toss a little more in there, I'm also pretty interested in the Diplomacy and Affiliation arcs. Unfortunately both these and the "dwarf mode autopilot" necessary for meaningful back-and-forth between adventure and dwarf mode strike me as somewhat less than immediate possibilities. Ah well, the current stuff looks awesome too.