there should be an evolution tree where you can customize how your species mate like:battle for the mate or dancing for the mate,your species at first have the basics meet a mate than mate but you could change the way your specues mate but took time aswell,these ways of mating could benefit your species like battle for the mate increase strength or singing making your species more intelligent,it needs time for the entire species to adapt to this mating style,but you change your species way of mating that isn't related than it will take a lot of time and you couldn't stop it.
I imagined some randomized fitness as a feature too. Mating displays can be one of the ways to pick out which creatures are more apt to give your next generation some minor advantage, or just some extra mutation points. Other stuff could be some minor Colour differences between different fitness levels of your species, different mating calls, and so on. Like how vibrant the colours are, or how well they blend in, or, the volume or complexity of their mating calls. Though I'm not sure how you could code that.