Bluski, Istanbul is an interesting one. Turkish Airlines are increasing Istanbul - Dublin next year from daily to about 10 or so a week. In an ideal work if the likes of the DAA have their way your choice from Cork to Istanbul will be via walking, biking, a donkey & cart, a car, a bus or a train to Dublin Airport for the THY flight to Turkey. I would bet that your hope via Cork to Frankfurt to Istanbul with LH would receive little encouragement when there extra flights to be filled ex Dublin?
There are certainly enough Asian folk living in the Cork and Munster area to justify trying out a direct flight to Istanbul at two or three a week for connections to their mother countries elsewhere in Asia etc.