If the original host is the one that needs to disappear I would TEST this workflow...
1. Host starts event
2. New person that needs to host either reclaims Host role with Host Key, or current host makes that new host the host. (if the new host is a attendee, they have to made a panelist first)
3. More than likely the OLD host will still show as a Panelist so the NEW host will have to right click on the old Hosts name and then Change role of the OLD host to Attendee.
4. When OLD host needs to be the host again, they can either reclaim with the host key, or the current host can elevate to Panelist, right click Change role to Host.
The host key is found in the event information of the person that scheduled the event on the Webex site. Log in, locate event, click on the event and the key is listed there. Host key is applied in a live event by any attendee or panelist by clicking on the Participant drop down menu in the top left menu bar. "reclaim host"