I've been thinking about the same. We (three boats) did Turkey in October and really enjoyed it. The Med sailing is much different from BVI - distances are longer and depths are far deeper. Almost no mooring balls, so all anchoring and med mooring. Wasn't a problem with the Jeanneau 64, it had 300ft of chain. One of the other boats only had 100ft and that was a challenge. Once you get the hang of med moor it isn't so bad, but it can have a steep learning curve.

License wise - you will need an IPC at the minimum - if you are ASA103/104 or US sailing bareboat grad they can facilitate it for you. First time I've had to show my credentials in a decade!

I'm thinking of chartering for a week out of Lavrion and sailing around the islands. You really need two weeks to cover the area though. Send me a DM if you're interested in joining up as a flotilla. I will likely have 2 or 3 other boats with me - I am an Instructor for a couple sailing clubs.