Currently Settlements are all the same essentially. Dwarfs have their unique thoughts and friends, but they are no collective of any sort. They share nothing, no drive, idea, value, everyone is just minding their own business. If you have an idea for your fortress, it is yours and the dwarves dont care, even as they execute their tasks to accomplish your plan for them.
So what if your group of settlers could dispatch for any other reason than colonizing?
To do that properly, it would probably require a little bit of prologue.
A few things I came up with :
Pologue: Last survivers of a ransacked settlement
Starting conditions: up to 15 dwarves, many injured or crippled to some degree, low cap for pre-existing rations and allover weight of starting items since they dont have a a cart.
Goal/Drive: Survival and safety from attackers, revenge on the invaders.
Result: Since they survived an attack by humans, they now have deep prejudice against them, war on all humans would make the survivers happy. There might be criminal incidents of dwarfs attacking human visitors. A large army, attackers dying and a good stock on food gives them more intense happy thoughts. People dying/being snatched from attackers has an even worse impact on them.
Or:
Prologue: An exceptionally greedy bunch got expelled from their homelands
Starting conditions: They brought their possessions, which is high value material, but there is a limit on many practical items as they were traders, not workers.
Goal/Drive: Archive high wealth and do anything to constantly increase it
Result: High value surroundings give them extra happy thoughts, vice versa with rough/low value surroundings. Room quality affects them more than usually and they have higher standards.
Then there would be the question on how much can/should be pre-defined or player-choice and how much of it can or should be be generated.