A union of Mediterranean countries would be a good idea for all involved. These countries have similar climates and economies, and a trade pact between them would make good economic sense. Economic unions tend to prevent wars since countries that do business together do not want to fight each other.
We are in a time when the economy is global. Countries can no longer be isolationists. They can no longer expect to be able to survive on their own. Everyone is making treaties and pacts with other countries to help with trade and pooling resources. I don't see a problem with that.