It's been a while since I was here, so many changes it will take me a while to catch up but all the idea's are good. I think that the hardest part of the game is how to figure out what it takes to remain human and have more fun, or be bad and still have fun. If you become something minor it is hard to get back to being human, the easiest way I have found is not to play for a while and tada you are human again.
I agree mom, the next thing I'm planning to add is some specific quests, or tasks for each creature. This will give you something fun to do (even if you're a say, a grasshopper), and when you successfully complete the job it will reduce a lot of your karma, and give you a better chance at human rebirth.