I would love to see some sort of job-related consistent stress. Job preferences, that sort of thing. I think the "been away from friends/family too long" stress moodle really needs adjustment, though. I get being away from your friends, but I've got dwarves that have been living in my fort for 15 years still depressed because they emigrated away from their drinking buddies in the hillocks over a decade ago. Even with the dwarven lifespan of 160-180, that's a *long* time to make new friends and get over your old ones. Then, of course, there's the "hasn't acquired something in too long" and the "hasn't wandered in too long" which seem to be mainly the fault of the dwarves themselves. They are carrying rings and bracelets and pants around constantly, why don't they grab one? It's rare that trinkets are actually important, and I don;t really have a stockpile of them for any reason but to have them. Maybe this is a holdover from the economy days, but I think for now it would be prudent to have dwarves go and claim something from the trinket pile (if there is something there) every season or however often it takes to keep them happy, as an actual need based job like "eat" or "drink". The wandering thing I just don't get how to fix, it seems like it's their choice to spend every moment of their free time stuck to the tavern stool. This also applies to some thinking thoughts ("hasn't thought abstractly in too long" -- the library is right next to the tavern and we have literally the largest single book collection in the dwarven world!), but those might be fixable with the right job assignments.
I would love to see some sort of emigration mechanic where unhappy dwarves leave. Or where they occasionally petition you with a specific fix to their unhappiness, because half the time it's an educated guess even with the wiki. Seriously, if I had a dwarf come up to my mayor and say "Can you put a rose gold cabinet in my bedroom? I'd love that" I'd do it.
Also, some kind of catharsis mechanic for after mental breaks, like rimworld. I've noticed a few dwarves falling into a cycle of throwing a tantrum, then feeling bad that they started a fist fight/broke something/got the crap kicked out of them, so they tantrum again, so now they're sad that they started a fistfight (x2), which makes them tantrum again, repeat. So far, they eventually make the mistake of tantrumming next to one of my professional military and get beheaded, but until that happens, they cause all sorts of problems.
Side note: I have found that having all of my dwarves in "practice squads" that train 2 months a year (might cut it down to 1) on a rotating schedule seems to make them a bit happier, because they get combat skills somewhat regularly (1 level in 1-3 skills per training session is common) with a squad leader from my pros, and the happiness boost from improving a skill seems to be pretty big. Leads to a bit of frustration as I wait for my manager to free up and accept orders, but I've distributed the professions around enough that I (mostly) don't get slowdowns. The few times production stops is when I *need* my best craftsdwarf working, like when making weapons and armor.