Using built in WP settings and functions you cannot do this.
It is especially difficult because you want this to work on the front end of the site and at this point there isn’t any way for PHP to know what editor set the time.
The best solution that I can think of is to add a new field where the editor can select a time zone, like a select field, and have the values of this field match the format of the default time zone setting in WP. Then use this new field value to replace get_option('gmt_offset')
You could limit the select field to only those values you need and have the default be where most of the editors are located.
