Wait so now you get better control over traits and nephs builds?
Does the breeder having certain traits mean you can breed for more specific things?
I don't really play the game that much. Do you still need to be a futa to get Unicorn neph?
You can now find recipes to give to the new cook npc, Bryn, who then sells foods that give and raise ranks of specific traits. Envy, the new demon npc, can remove traits given to the breeder, but I haven't tried that out yet, so I don't know specifics for her.
There are foods for the Melding and Influential traits, which raise the chances for hybrids and the offspring being the parent's race respectively. You can give foods to your nephs too, so you have far more control for breeding and traits, but I don't think you can remove a neph's traits in any way.
If you want your breeder to be a parent of the Unicorn, your breeder needs to be female or futa since there is no male spirit form for mares or elves. You need to have at least one futa involved to make a Unicorn.