Half measures undermine the authority of the coach, who will already be part way there with the title Interim in front of his name.
Pick the assistant to fill the role, sit him in the chair, move one of the junior assistants into the box, and external to this the board can start the replacement process. That's all that needs to be done for the rest of the 2015 season.
Probably right. Just thinking it's a lot to have to prepare for in the space of a week.