Istanbul is pretty much a trans-continental city with much of its urban sprawl taking place on both sides of the Bosphorus, as well as a significantly large populatuon and economy, as well as being the center of Turkish culture.
Should Greece reclaim the city (and Adrianople) some tine in the 20th Century, how would it rise to the same international prominence and vue that Istanbul currently has?
A large portion of the city's population came from rural Turkish settlers after the fall of the Ottoman Empire. Applying this to Greece seems hard as the Greek heartland isn't as populous as Turkey.
Maybe a significantly larger Greece (Megali Greece, perhaps?) could attract the necessary economic investment and population source to concentrate on the city? Or making Constantinople the capital/refugees from Russia and the Balkans serve the same purpose?