Hi, long time lurker, first time poster, here with a suggestion.
Basically, I read a little bit on the various improvements planned for squads and their control, and one little bit in particular caught my fancy - the part where the squad is separated out from the individual dwarves it consists of. Which is cool not only because it allows more control and whatever, but it also (maybe?) allows the squad itself to become an entity that can have a total kill list, maybe even compete with other squads on that count?, and become an historical entity, depicted on engravings and etcetera.
Anyway, my actual suggestion is implementing something similar - groups of various sorts - into the non-military section of the fortress's populace. Such groups should not be created upon the player's wishes, as squads would probably be, but rather when the dwarves themselves get to it. These groups would have different objectives (ammassing wealth or objects of a particular type, growing in numbers, killing things that look at you funny, creating objects of exceptional quality, and so on), different ways of member growth (recruitment along skills, dwarven psychology, being born into it, performing a special action, or non at all) and different ways of getting triggered.
For instance, several dwarves who like helping others could form a charity, bug the rich for money (imaginary credit, whatever) and hand it out to the poor. The Nist Akath Fairsabres clan would be an actual clan in the game, with a reputation and possibly belongings of its own. Cults or religions could start when an a special item/creature/place is found/created, or when believer manages to pull off a minor miracle. And, of course, guilds could be reintroduced (rather than a representative trekking over here, the first legendary something may have a chance of starting his own...).
And, of course, these groups should be able to have relations between each other - friendships or, more interestingly, grudges - both of the fisticuff and rivalry variety (A dwarf could possibly belong to different groups, with an unhappy thought when the groups he belongs to are at odds with each other).
Methinks this would make the late game a lot more interesting, changing the social structure of dwarves from legendary crafters - military - hoards of useless peasants to something more complex, and more story-worthy.
Ideas questions comments?