Originally Posted by
LHR/MEL/Europe FF
Exactly my thought. Any country that requires a visa, visa on arrival, or even pre-registration of some sort, is going to be at a significant disadvantage as a hub.
Vietnam does airside transit without visa requirements, and a lot of countries have visa free (and pre registration free) entry to Vietnam for up to 15 days Only requirement is that it is 30 days since last entry.
The Vietnam E visa application takes about the same time to complete as an ESTA Though unfortunately, the e-visa only offers single entry at the moment.