I think it's a great and compatible idea for this theme ! But considering that there is a short time left i think you need a more playable and designable mechanic so in my opinion you can create different challanges for different creatures, if you design these challanges in such a way that at some point the creature will surely die you can respawn the player as a different creature based on how many karma scores the player have. These are the only ones that come to my mind for now. I hope it works for you, good luck!