Taiwan, Vietnam, Laos, Thailand have already gone with Standard gauge for their new railways.
The Japanese Shinkansen is standard gauge system which is separate to the rest of the narrow gauge railway network in Japan.
China and Korea already use standard gauge for all railway lines.
Even India will be using standard gauge for its new HSR lines.
Moving towards standard gauge is the norm in Asia.
Indeed, but you can use a little bit of narrow gauge to start the traffic going, once that’s established and growing you could use PPP to upgrade to standard. This is what is happening in Africa. They are building and upgrading narrow gauge for this purpose. It is very effective, is low hanging fruit, brings early harvest, provides commercial validation etc..
For Indian highway proposal, it’s important to remember that China doesn’t just build highways, they build economic corridors.
Along the highway or railway is a swathe of other infrastructure such as new towns, local road networks, 5G, Covid-safe warehouses and food storage/transportation logistics suitable for import to China and even dams, data centers, and HV power lines.
Can you imagine what would happen to an Indian government if they started building that stuff abroad?
Check out this relocation village in Laos,