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.

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.