However, the human genes in their world differed from those of humans in other worlds. In theory, every human in their world was a potential ghoul. It was just that, without some kind of special stimulus, these humans would never become ghouls in their entire lives.
Ghouls were more like a special subspecies that had branched off from this world's human population. But at their core, they were still human—they were people from this world who had changed.
In the Empire, there was a caste system.
The castes were divided according to species, and the standards varied between species. Of course, if an entire species had exceptionally good genes, like the special species created by Uchiha Brahman, then it would basically have only one caste.
Because the ghouls of this world were a subspecies branching off from humanity, when the human production machines were built, no special production machine would be made for ghouls. Only machines for producing humans would be built.
But that raised another problem. Under natural conditions, it was almost impossible for an ordinary person to become a ghoul. Yet, at their core, humans could indeed become ghouls. This would cause problems with the caste divisions of the human species and could even affect its potential.
As for mixing ghoul genes with those of primitive humans and cultivating them together, that wouldn't really work. Though there wasn't much reproductive incompatibility between ghouls and humans, doing so would be too troublesome.
Since ghouls were fundamentally human, any human could potentially become a ghoul. If ghoul and human genes were used together in cultivation, there would be no element of chance, no feeling of opening a mystery box. Uchiha Brahman would not allow that.
After all, this world wasn't the Shinobi World, with its vast array of Kekkei Genkai