I would like this too. Here's how it can work:
1. Customer sends email to osTicket.
2. osTicket checks if there are any email addresses in the cc field and puts that in the column cc.
3. When the ticket is replied to, email is sent to the person who created the ticket and the email addresses in the cc field.
4. When osTicket parses the email's cc field, it should remove any email addresses that are invalid. IE name . That's invalid because the email address didn't contain the @ symbol.
5. When replying to a ticket, staff should be able to remove emails from the cc field if they need to and it will be permanent.