Unfortunately, the OSD process is not set up to utilize the serial number as a valid machine identifier. The current targeting mechanism which relays the machine script request to the core utilizes the MAC address which is then converted into a machine object that relates to the existing inventory records. Due to this mechanic, MAC address is the only valid machine identifier to launch an OSD tasks against.
Are the MAC addresses in some form on a barcode available on the system or on the box?? Otherwise you could use the Managed Planet DTS solution to scan those into the database...