That would be cool, a MC server for only CHU members. Would limit the griefing so would make for better game-play. There are a few servers out there that do have interesting game-play.
There are some servers that are devoted to building advanced, complex and huge structures. Ranging from things like castles with all advanced things you can think off to add to it. To things like a giagantic replica of some space ship from some TV show or movie.
There are also servers that are more Role-play based, I know what you are thinking. That it sounds gay, commonly I'd agree but there are some that are decently fun. One is called Tribal warfare or something like that. A fresh map is generated on the server, you are assigned to a team and each players has nothing at all in there inv. Each team finds a location to start out in, they then do what they would do in minecraft singleplayer except with teamwork with other players. For a example, one player would focus on collecting wood, you may have 2 players mining and the fourth collecting food/other things. When they get the resources they need, they start building there village, castle or whatever. They always try and make it as advanced as they can. Including building many traps for the enemy team(s).
Each team is working against the other team and at any time can sabatoge them. Either by wandering over to there village, sneaking in and attempting to steal there resource supplies or building traps in there mines, there village, etc. Ventually each village will get equiped with swords, armor, bows, etc and look to take on another village. If a enemy team is succesful in taking out another village. They in general capture it, making the players of that village work for them. Which means more resources and fighters. The team that dominates wins.
It's pretty interesting and fun, there was a mod like that for WarCraft 3 that was extremely popular.