IS IT AN ADVANTAGE TO HAVE ALL CUSTOMS DEPARTMENTS WORLD OVER BE GOVERNED BY WCO ?

Generally Speaking, Customs already is governed and guided by WCO. But each and every countries have their own interpretations and implementation of Customs Rulings, which sometimes ruin the fast flow and movement of Trade. There should be strict implementation by WCO of certain Rulings such as Country of Origins, Markings Etc, which will be a standard guideline to be used and followed by all exporters. 

yes it is at least the customs department can take any update for customs Tariff or the prevented goods or the Endemic countries