So its irrational to fear that a ball python may latch onto a kitten? I dont agree. A kitten most certainly could be grabbed by a ball. Now if it was a grown cat I would be worried for the snake.
Cats will be cats and they like to play, catch, and kill so I say keep them apart. I have never seen a cat or snake that was trained to drop it, leave it, or release. So getting them apart if they lock up is going to be tough.
There is nothing to gain from this and its not worth the risk.