There is always the issue of multiple accounts on this site and from what I can tell it's all based on the same IP Addresses. What about people who live in the same household, that both enjoy, and want to pay for CC?
My suggestion would be to have a linked user option, something like adding a friend, only you add the account with whom you are linked. Say each user is permitted to have one linked user - Then create something on the back end (I don't know how things are coded here) that disallows linked users to play in a game against one another that has more than two people in it and only allow linked users to play against each other, or on the same team in a teams game. That eliminates any possible secret diplomacy issues.
For example, two accounts - fookeh and some_cc_account... provided both accounts have a premium membership, can be linked together (done similar to adding a friend), and cannot play in a game with more than two people (can only play against each other if playing in the same game except for team games). That way, there are no secret diplomacy issues and no cheating issues.
If this suggestion is rejected, how could two people who just want to play and have fun on here play together, but live in the same household, other than having to use a work pc on breaks?
Thanks for your time folks!