I was hoping to rp it as dwarves in your fort getting married after knowing each other for awhile, but I guess that's true that random people could end up getting married after only knowing each other for a few days (especially after a migrant wave).
Generally, I would expect most dwarves in a typical fortress to have precisely zero friends. So you could limit it to among friends, but that's going to cut into the 1/3 ratio.
On a related note, if you marry 1/3 of population off each time, by the fourth year there's going to be near zero suitable matches, barring migrants. The greater the initial effect, the sooner the pool of singles is depleted.
I was also thinking of maybe a way to incorporate contracts, boundary disputes, agreements, etc. A holiday where people are all about making oaths and signing contracts. Could have diplomats and outpost liaisons from all of the civs you know come to make deals, talk and discuss things?
The reason I didn't think of anything but marriage was that the current diplomatic/ownership system is fairly barebones. There's trade agreements, and civ relative relationships, and in fortress individual dwarves may own their clothing and some trinkets.
So all such oaths would have to be constructed from the ground up. This may prove...difficult. Villain update might make it easier, with individual positions having more responsibilities and abilities so that they could misuse those.
Yeah. I was thinking ghosts and other things coming back to life (maybe reanimation for the day or slabs breaking?), spooky stuff, but I dont want to create too much issue in the fort where the holiday becomes more of a pain then fun, causing tantrums and such.
I could change the holiday to be more about ancestors though. I could create a new friendly ghost creature that doesnt scare people and have a bunch of those show up as visitors.
Built slab destruction is going to result in murderous ghosts (even if the ghosts initially wasn't murderous).
So yanno, mileage may vary. It rather stands out amongst all other holidays which are generally fairly positive.
An untouchable "ghost" visitor - potentially with the soul of somebody lost in fortress - would be neat way to make the interaction visible, though I fear it would result in no actual interactions unless forced to stand next to their bereaved.
On that note, this does also bring up the importance of player participation/interaction in the holidays.
I like this idea. I wonder if there is a way to make this day beneficial for farmers to plant seeds? Maybe a bonus to the grow skill temporarily?
Could work. Alternatively, seeds in farm plots also have planting skill set, and of course the plots themselves could be fertilized as well. This is going to be fairly easy, but I fear also fairly unnoticeable. Something like trees unseasonally growing fruits would be more visible, but that plays more into harvest.