Really like this and see so much potential.
I have two suggestions:
- Currently most of the traits fall into two categories. Genetic (e.g. Hardy, Swift Womb) and personality (e.g. Doting, Aggressive) traits. I would separate those and mechanically differentiate how they can be acquired.
Genetic traits are obviously already given as how they should be.
But for personality traits I would introduce a stage for individuals were after they're born they first stay in the pen for a day and whichever adult is together with them has the opportunity to impart their personality traits to them and a smaller chance to give them opposite personality traits.
There are some traits which fall outside of those categories (like Virgin and Lucky) which have the vibes of being bound to specific conditions. I don't want to propose a solution for those but they can just sit in their own category of Conditional Traits. This would also open up possibility for some new temporary ones like Enraged, Miffed, Scared, Scrawny or Chubby.
- The Vigor, Fertility and Beauty scorings are currently just numbers. I would have them be a calculation resulting from specific traits. Some of them beneficial like Strong Muscles, Hyperspermia (Male only), Hyperovulation (Female only), Rosy Cheeks, Voluptuous Hourglass Figure. Some of them malignant like Frail, Lazy, Oligospermia, Endometriosis, Asymmetric Face, Scaly Skin.
So a perfect 100 would a combination of all the good ones of that category without any bad ones. And well, the baseline would need to be at 50 (with no notable Traits) or it would have to be able to display negative Scorings.
This offers the opportunity to tie more traits to dynamic graphical representation of the individuals (you already do this with some like Golden and Abyssal although those only affect color palette).
Of course then there's the argument "Beauty is subjective." and "Flavouring these as bad is discrimination." So there needs to be an inworld exlanation like "The calculation of Beauty is determined by the personal preferences of the demon lord and the Market agrees with him out of fear."
But of course those who come to you directly with contracts have their individual kinks, sometimes look for something off the treaten path and will voice their adoration for them. To lean into this then fulfilling contract requests quickly could entice those who made them to reappear more often giving a Breeder who wants to fill his roster with a specific kind of individuals the option to stay profitable without submitting to the general consensus (maybe they could even grow influential enough to convince the Demon Lord to change his preferences).
Sorry for the wall of text. I love to ramble.
And I would totally understand if you'd consider pursueing these suggestions a fruitless effort.