Hi Aniket,

There always exists one 'System Administrator' profile with admin & security_admin role always for all instances. This can be used as 'Run as: ' User always for any background scripts.

Also, since you would be using Scheduled job better do a check for the script in background script to ensure the count of admins you get so as to ensure that when script executes only the invalid ones are revoked from Groups & Roles table.