I am proposing a switch away from constant simulationism in fortress mode, with the great bulk of time being passed in a less active state not entirely unlike a city simulation -- but which can, at any time, at the behest of the player or the world, shift back into simulationism.
World time advances 72 times as fast in fortress mode as in adventure mode, per tick. We all recognize how strange it is that a caravan takes three months to go a distance an adventurer can take on foot in an hour, or that water takes weeks to flow into a new basin. Brushfires, combat, travel, and hauling all suffer. One booze roast will keep a dwarf chipper for a season.
There's a lot of abstraction at play, and that's a good thing. But when it gets in the way of content that Toady wants to add, we have a problem. This will keep caravans from being consistent: traders will travel at adventurer speeds until they come to that one magic fortress the player controls. This will keep sieges from making sense: the vile horde of darkness burns its way across the world, only to crash up against the time dilation of one last fortress. This will force all kinds of compromise into the upcoming adventurer skills: plant my crops, and now what?
Do away with the lie entirely. Embrace the hierarchy of scales: simulationism (adventure mode) at the bottom, then daily life (fortress mode), then world-scale (caravans and armies), then worldgen itself; these can be united into a coherent whole, where certain circumstances at a higher mode of abstraction trigger lower modes of abstraction. Sieges and the arrival of caravans are familiar instances of this, where the abstract world-scale arcs impinge upon the simulationist life of the fortress.
These subsystems can all run at all times and defer to each other when necessary. Imagine if those battles in the legends all really happened. "I am Othgul Morulgul, slayer of Pithic Ternisin, whose arm I severed with a steel battle axe and wielded as a hammer to drive his left floating rib into his lung."
So when the caravan comes, you get a message and time becomes real, or when that vile force of darkness arrives, or when a section of the cavern collapses. And in principle, then, your adventurer and his cohort could shift into fortress mode at any time, to wait for crops to grow, or Toady could let you (the player) seize control of any dwarf in the fortress.
It's hard to write something like this, but it's harder to write what Toady's writing now. There are plenty of advantages to be had from such a change, from a more consistent world, to less loading lag, to pathfinding improvements (dwarves don't need to be omniscient and can operate on habit and incomplete information even under full simulation -- many optimizations become possible), to more meaningful appointments as an arsenal dwarf actually interacts with other dwarves to get equipment where it belongs. If you don't remember this from DF Talk 4, go to http://www.bay12games.com/media/df_talk_4_transcript.html
and search for "The whole Dwarf Fortress time dilation is always going to be one of these big thorns in the side of the game."
What I'm curious about, then, is what gameplay changes you would expect from something like this, and whether you'd expect it to make the game more fun.