Since I'm directly related to content added intothe game:
1. Thats a lovely Idea, but I'm not touching those glitchy models, but perhaps some time, some day...
2. Yes! We could do such a marking ^^
3. No-yes. Not hair, obviously, perhaps more paradisy haircuts. But tails currently used as neck ruffs can and will get new models like more ruffing and tail feathers in future updates. And tufts for wing feathers yes and yes, yes.
4. We can't transfer the penguin heads to the other bodied models due the way they were made.