See my last post with Ryouichi. It practically is the fill in for what has happened, and what will happen.

As for Myojin returning to Vice-Captain position - maybe, but maybe not in 10th.

One suggestion: if Dorizzit is okay with the Ultimatum Ryouichi gave to Damara, Myojin could become 6th's new 3rd seat, and eventually Vice-Captain. (Practically, he'd be Vice-Captain from the start, since 6th has not had Captain proper for the whole game.)