Would Constantinople become a vast urban battlefield?

Could the Ottomans have defended Constantinople and turned it into the largest urban battle of the war?

Probably not; the Ottoman court would likely abandon the capital once the Allies forced the straits.

A successful passage of the straits would probably avoid a destructive urban battle for Constantinople. The Ottoman leadership would likely abandon the capital once the Allied fleet broke through. Control of the city would then be settled by the victorious coalition. The timing still matters because an early capture leaves Britain and France more options, whereas later success comes after Constantinople has been promised to Russia.