That I don't believe. Well, I believe they are locked to certain variants, and currently we players cannot access that part of the game. So in that regard, they are inseparable, right.Any features that Nephylem or the MC has can not be transferred to others purely because those features are not a seperate entity.
But mechanically, visually - looking at the female hominal body model, it's basically the same as the breeder. Maybe modfied by some templates like chubby for giants or slimmy for tabbies, but ultimately it's all the same base female body mesh. Only difference is the attachments tacked on to different species & variants. I mean, look at the human-cock futas without any pubic hair to cover the seam, them dickies look like glued-on dildos
Even with current limitations, you can make a bunch of spirit forms with the same base female body as your breeder, but different animal cocks slapped on it, as I worte above. Use neph species that DO have animal cock on hominal form as base, remove all attachments & skin textures, paste human breeder shape & color scheme, fine-tune color & shape, done. Currently has horse, bovaur, foxen, vulwarg, demon and dragon cock on human forms in my spirit form repertoire.
Same goes for all other "attachments" -I count everything that isn't part of base body model under that, arm/leg style, horns, ears, tails, wings, hairstyles, dicks- which could be looked at basically like clothes in an NPCs inventory list. You can already set all of those to "off" or "invisible" in the editor, and with access to the individual NPCs in the code, it would be an easy feat to add or exchange pieces as well.
All I'm trying to say is, technically it shouldn't be too difficult, Dev (or some crafty modder) could likely implement "interspecies dick exchange" feature with a few clicks, like adding piece of clothing or equpiment to an NPCs loot list...so we all know it probably ain't gonna happen anytime soon, right