Wrong Approach
Shutting an engine down during taxi in on a twin to save fuel, is about the same as sticking a bandaid on an arterial bleed . It might seem like a great idea at the time whilst sitting at a desk but it ain't going to solve the real problem
The single biggest waste of fuel is the result of an inefficient ATC system in HK . I know that HK ATC controllers are doing their best within the confines of their geographical location and limited airspace. But every time I go into the hold for 10 -20 mins, or get vectored all over the South China Sea at 10,000 ft or lower in many cases, the amount of fuel wasted on just one flight dwarfs the entire amount of fuel that I'm likely to save with this ill planned idea.
But hey if they want me to kill an engine and run the other one at much higher thrust just to keep moving I will .
Now if they wanted to make a difference, tow us out to the holding point before we start, that might save a bit of fuel especially in JFK . I'm sure JFK ground would be more than happy to accommodate us in this endeavor