i have info to add. i think it spoils from the manga. but it's very, very minor and shouldn't interfere with anyone's enjoyment of the anime.
they could always "un-disgrace" the Shiba clan and make Kuukaku a captain. she's probably qualified, even if she sin't technically a shinigami. and if they want to really mess the anime up and differ from the manga, they can bring Ran Tao back and make her captain of 5th Squad. or some such nonsense.