3: IMPREGNATION mechanic - It'd be nice to see that if a monster creampies your character, she sometimes gets a swollen belly the next day which slows her down and makes her lust rise faster, then having her give birth the next time she goes to bed. Now that on its own would be enough to satisfy me, but this could be made into a further survival mechanic: if you instead give birth in a monster pen, you get a resource-producing critter who turns food into crafting materials every few days, but will try to fuck mommy when she goes to check on her harvest. Naughty, risky and useful.