Mod request: a different kind of birthing mod

This may seem like a strange modding request, but for fantasy and sci-fi game play I thought it would be interesting if sims could have the option to lay an egg that could birth into a baby sim. I felt like my Naga and alien sims are just missing something when it comes to child birth options but I'm not a mod creator and have no idea how I would go about making something like this.