Kovu never realy wanted anymore animals realy, all he wanted were just the canines and felines. besides the sparkle floofs, I reckon this game was meant to stay more on the realistic side of things.
it would also cause alot of powerplaying, like dragons ripping other animals to shreads, because they think they are all powerfull, and rule people.
I personaly dont feel its a good idea, but thats just me.