I'm surprised that many of the initial responses were just to "leave the clan and join another one" or "just start a new one"! In the first case, what happened to clan loyalty?? We have a solid and active group of guys - it would be a real shame for everyone to scatter to the four winds because there isn't a way to replace an inactive leader. In the second case - yes, starting a new clan would be a viable option, but not without losing all the progress we've made to date (we're nearly a lvl 8 clan). Starting from scratch would be a huge discouragement.
Seems like a simple solution would be to give Co-leads some real power instead of just a title. Let me preface this by saying I'm not a Co-lead (I can't be made one since our leader is afk), so please correct me if I misrepresent anything. Maybe take a cue from other successful games such as [edited]and at least give Co-leads the power to promote/demote other members of equal and lessor rank, change the clan motto, etc. Hopefully when the clan wars become a reality, Co-leads will be able to initiate them (again, in [edited], a co-leader can initiate a clan war). With these minor changes, a clan can live on and function fairly normally even if a leader goes mia without transferring the leadership title before he goes.