LUST_PROPENSITY is already a personality trait, so why not do something with it? Introduce needs and values related to sex!
Tirist McRepressed is constantly ablaze with lust, and he is conflicted by this because he values chastity.
Rakust Kinkyboots is aroused after being chained.
Urist McHorndog is distracted after being unable to clap cheeks.
It sounds actually a good idea.
To make it bad: nobles are sometimes wanting a metal they shouldn't logically know, such as slade. Some dwarves could lust over persons they cannot access, either because they live in a place they wan't go, they are dead or even they don't exist.
Yet, which brings me to the following suggestion
Tulpas
When enough creatures in the world think about a currently no existent entity, that entity spawns within your fort. Whatever it is is usually some mythical Forgotten Beast or clown, these creatures will intimidate the populace of the fort to begin to, and continue to, think about them so they retain form. If members of the populace begin forgetting or adding details, the original will change form based on how the population thinks of them. It doesn’t kill those who think about it, even going so far as to protect its thought sources from other invasions and against other tulpas’ intimidation attempts, as when a tulpa is comp,Evelyn forgotten, it simply fades away. Members can think about multiple tulpas, even dreaming them into existence when enough have a shared dream. The more tulpas who exist in a fort, the more likely the fort will spawn more tulpas. Additionally, tulpas can spawn in the world too, every creature, including sentient ones like dwarves, elves, goblins, koboid, humans, and others, can be tulpas. It might be possible to have a fort with tulpa dwarves, so you will have to remember which ones are tulpas and which are not, because if you only have one dwarf thinking of all the tulpas, if that dwarf dies, the tulpas die too. Tulpas can think about and spawn other tulpas, but they of course cannot feed on their own thoughts. There could be whole cities inhabited be tulpas, all thinking about each other to keep everyone alive, and trying to get your adventurer to think of tulpas too.
New mechanic: memory limit, creatures with higher memory stat can store more memories without having to forget them. If one is at their max memory, thinking about a new thing causes them to forget something else. When a dwa4f is attempting a task, thst task takes up a memory slot. A side effect is that if all a dwarf remembers is various tulpas, it won’t be able to do anything else, and as such needs to be cared for by the tulpas it is sustaining