User blog comment:HollowKing17/Vacant Captain and Lieutenant positions/@comment-7092747-20130609224315

We have to remember that Tessai and Kisuke were banned from the Soul Society not by Yamamoto but by Central 46. While Kyoraku has shown that he is not afraid of defying Central 46 to get things done, he still cannot defy them as a whole and the ban they set in place (at least the Central 46 that existed before Aizen killed them) likely has no interest in lifting the ban on either individual.

Hachigen actually would make a sound choice for captain of the 4th as his kind demeanor and mastery of kido would fit well with the position of leading the medical ward.

As for the 8th division captain position, I highly doubt Isshin would return to the Soul Society and abandon his daughters. As for Ichigo, his concern is in protecting his friends and family so leaving for the Soul Society full-time would prevent him from doing so.

For 8th vice-captain, it would be very possible for Lisa to return to her former post as we have seen many of the visored return to their previous post.