Why not make a new account for this user which will generate a new database ID. Then delete the user with the ID of 1 and attribute all posts / content to the new user you created for them? Then you don’t have to worry about queries or messing up your database. Also, as said before this makes absolutely no sense from a security standpoint as it’s pointless. If your client doesn’t trust you enough and wants to micromanage the site security they clearly know nothing about, might be time to dump that client.
