Very realistic option! Unfortunately, Keeping access roads to it open, year round will be another issue.
@krash Input please
Most of us are just drawing lines on the map and expecting to run trucks over them. It's not just the 15km stretch that we would need to tunnel. Our side of the border is made of +7000 meter massifs. This was taken looking back at Pakistan while standing on Noshaq, which makes up the border. All this would need to be tunneled under.
Unlike the KKH, and as you rightly stated, most of the approach to get to this tunnel will be snowed shut for at least half of the year.
Then there's the other side of the Wakhan Corridor which has no roads, no infrastructure, nothing. All of it also receives massive amounts of snow and is high altitude mountainous terrain. The
only road running through it (which would either take you North to Uzbekistan through Kyrgyzstan, or West to the rest of Tajikistan), the Pamir Highway, looks like this,
This stretch is longer than the length of the KKH on the Pakistani side. It also passes over the Ak-Baital Pass at 4600 meters which is shut, just like the Khunjerab Pass, for most of the year. Btw, this is what most of the "highways" in Central Asia look like, except the ones China plans to build. Even up on the Steppe.
If it's just about drawing lines on the map then the KKH passes around 5-10km from the Tajik-Chinese border. Better we connect it there.
You don't build trade routes through these sort of mountains unless that's the only option you have, à la the KKH. Certainly not if you don't have anything in your pockets.