Based upon your request,
(1) Unfortunately, there is "NOT" a lot you can do.
(2) 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 make the change.
(3) Other matters would depend on your clans development.
(4) You would have to consider any stronghold commitments and if you have elders they can accomplish most things that the chief can.
(5) If you are a very active clan, and do well in the events, or actually win them, then its a bit "pointless" continuing the same clan as you would not get the rewards.
(6) You may need to start a "new clan" making provisions that history cannot repeat itself.
(7) If you do have a workable stronghold, for example a level three, rather than abandoning it, you will have to maintain access to it in order to get its benefits.
(8) If the clan chief has quit for good and has not left an "infinite shield" nor "demolished" the buildings, you can farm the town.
Thank you in advance for the detailed information.
Best regards.
Lisa Brickfields