When Chief quit the clan he is obliged to make someone else a Chief, otherwise, he can't leave.

Problem comes if the Chief just gives up suddenly or cannot play for any reason.

plarium say that they are willing to remove a Chief who is inactive.  How long the inactivity has to last and whether plarium is always willing to do so or only occassionally I do not know.

Insted of making 2 chiefs, impement a takeover or a rebelion. If the Chief is offline for 30 days or more the lower ranks can pay gold to overtake the clan as the new chief. The lower the rank the more gold he needs to pay to overthrow the leader/chief.