To be honest, here’s what I can say about this from a technical point of view:
Blood and wounds as decals/textures: quite feasible
Dismemberment: Almost IMPOSSIBLE. Standard methods of creating this through preset parts and models clearly don’t work here, since the organisms that thrive are created by players/generated by auto-evo. The only way to implement anything even remotely similar is to create a dynamic dismemberment system like in Metal Gear Rising: Revengeance. But are you absolutely sure that trying to replicate an incredibly complex system that NO ONE has been able to replicate in 10 YEARS is a good idea for a small indie studio?
Sexual intercourse: Very difficult. Since it involves two creatures that can have absolutely any structure, it will be very difficult to implement, as the algorithm would have to automatically generate the animation so that they don’t fall into each other, don’t fall through the ground, don’t break their rig, don’t break their model, and don’t make unnatural movements. Besides, I think the player will only watch it a couple of times, and then they’ll skip it, like many other cutscenes.