This would be amazing if you could somehow get your male breeder into the receiver role to a futa nephelym giver. Has anyone figured it out? Fuck, I'd pay for that.
Sadly, that's impossible. Game's hard-coded to only list fem/futa as receivers, and creature's looks are tied to its sex. If it's a male, then it'll only look and act male.
The only possible way, and it's still a low possibility, could be changing creature's sex during gameplay, using CheatEngine or similar program.
Since body parts are loaded in dynamically depending on creature's sex and race, it MIGHT be possible to go to breeding, select fem/futa reciever, and, while it's selected, go to CheatEngine, find the bit corresponding to its sex, swap it to male, then go back in game and start the animation.
If character data is stored in memory as explicit strings, like in saves, then it's smooth sailing, worst case you gotta dive in hex values, character's unique ID and memory offsets.
I'll give it a try later and report back.