A small thought; what if there was a Noble or a job who's objective is to maintain the happyness of the other dwarves? A dwarf with this job enabled, or simply the noble in charge of these dwarves, would run around the fortress, attempting to make the saddest dwarf in the fortress happy. Sort of like a morale (morale as in happyness; not lawfulness) officer or counselor.
Primarilly, this dwarf would attempt to calm tanrumming dwarves, and would attempt to raise the happyness level of the dwarves in the fortress to the lowest possible "happy" level of emotion.
IMO, i think it'd make more sense for this dwarf to be a noble, just as the Sheriff /Captain of the Gaurd is in charge of maintaining dwarven law, so too would the Counselor /Morale Officer be in charge of keeping everyone as happy as possible. It'd also give a reason as to why the dwarf would need a office and cabinets; to do and store paperwork and emotional profiles. Being a noble also allows for their arrival to be predetermined, once X dwarves are in the fort, and to give the player extra abilities so long as that noble is alive -- like giving the player an overview of Dwarven Happyness :: Just as the Sheriff /Captain gives an overview of Dwarven Justice.
Once there's >75 dwarves, the job would be too much for one dwarf to handle, so like the Captain of the Gaurd, the Counselor /Morale Officer could mandate that he have X number of assistants; which would really just be an additional number of Fortress Gaurd soldiers.