User blog comment:Scott swag/Who could take over as captain cammander??????/@comment-1932702-20101019103507

Shunsui wouldn't be suited for the job. To be the Captain-Commander means taking up a LOT of responsibility, something Shunsui isn't comfortable with. The power of a Bankai alone isn't enough to make you a candidate because you need to have good leadership skills and the sense of managing crises without too much backlash. Besides, he would refuse the position on account of him being the laziest Captain in the G13 (which is why I like him anyways).

As Ukitake and Lia succinctly put it, there isn't a single person in the whole of SS who could replace Genryūsai Shigekuni Yamamoto.