just be careful on dropping the last leg - as it is breaking the rules of the ticket and has been widely reported over the years - that states roughly that all parts of the travel must be completed or the passenger risks the fare being re calculated and they poentially could request via the courts/legal means the payment difference. Its a way for poentially CX to reclaim some of the lost revenue on these error ticekts. CX is fully aware of who the travellers are and worst case scenrio is you don't want any legal issues linked to your passport when travelling thru HK in the future.