Hmm, on the fence for this one.
It seems VERY overpowered have both zombies and skeletons always follow rabbits no matter what. With cats added, there will be no threat apart from spiders, and they are passive during the day!
Although, I can see some upsides with this. If they still attract zombies and skeletons when they are sitting, you could make a zombie/skelly farm with spawners.