A downside of Diplomacy is it really only works with 7 people

If you are interested, there are variants on that site that have 5 people and (I believe) 17 people, although I strongly dislike them. Although WebDiplomacy has a vastly larger number of users, http://www.vdiplomacy.com/, a sister site built with the same open-source code has a great number of variants, and many people play variants there.

As a general rule though, I avoid variants, as they are not as balanced as the original game.

Also, and I'm going to stop making comments everywhere, there is also the gunboat variant, of which I am a large fan, where you're not allowed to verbally communicate, and all communication must be done through orders, ie. a support hold of another power to indicate an alliance.