The Ionian Islands were invaded in 1799 by a joint Russo-Ottoman Force to oust the French out of the Ionian Islands. What if at the congress of Vienna, the Ionian Islands were given to the Ottoman Empire as vassals only?
What role would it play in the Greek rebellion of 1821 for example? Would Greece be better off with an economically rich part early on as a part of Greece, if they become independent?