OK. Let me summarize: 

- This UI will be available in both order page and individual shipment page. 
- The difference is in order page, the "Ship order" button only appear if there is only one shipment. Basically it is exactly the same as shipping a shipment.
- Order status should be updated by shipment event handler as @winzou suggest. 

Thank you @winzou and @umpirsky !!