Do you think this Greece Travel Plan is feasible ?

You would need a vacation after this tour. If you cant possibly stay for more than a week, you will have to forgo some of this tour. I suggest that when you fly into athens, you should fly right to Santorini, A 35 minute trip. spend a couple days in santorini, then take a ferry to milos for a day or two. then take a ferry back to Athens. save Athens for the end of your trip. You can see most of the important sights in athens in a day or two. and be closer to the airport for your departure. I still say that a week is not long enough to go to Greece, especially if you have a long flight to Greece. Have fun