I think the best solution was to build two ports, one terminal north of the airport and another in the Saros gulf, and a direct and express railway. But this type of mega investment is not economically feasible as it would not generate urban rent and moreover we cannot forcibly close the passage due to the straits convention.
There are many academic studies on Canal Istanbul, the damage to the habitat has to be calculated really well. Even if we put aside the political debates, there are still national values that we are entruster of future generations. Not every issue should be approached with liberal glasses. A canal project that will not have the effect of changing the Straits regime will serve whom and to what extent, these are really important questions.
On the other hand, I must say that anyone who has crossed the Istanbul on the bridge of a freighter has learned from experience that the Turkish straits is probably one of the most dangerous strait crossings in the world. The slightest steering failure can lead to disaster. What's worse is that the freighters working to the Black Sea are really mostly junk ships. So the problem is not only the large vessels, any day at any time a major disaster can happen just like the expected Istanbul earthquake... We need to find a way to slow down the Istanbul strait traffic without antagonizing the Black Sea countries.
