Unfortunately,not a lot.
The clan chief is the only person that can nominate another player to take over, so you would need some way of contacting the old chief, and this person being amenable to the change.
Other matters would depend on your clans development.
You would have to consider any stronghold commitments, if you have elders they can accomplish most things that the chief can.
If you are a very active clan, and do well in events,or actually win them, then its a bit pointless continuing the same clan as you wont get the rewards.
You may need to start a new clan making provisions that history cannot repeat itself.
If you do have a workable stronghold, rather than abandoning it,you will have to maintain access to it in order to get its benefits.
If the chief has quit for good, hasnt left an "infinte shield" nor demolished the buildings,you can farm the town.