Any news on the server? As far as the construct goes my suggestion would be that the world with the tower is embedded in a normal minecraft world. If the gray space around the tower was used to host a city map then you could have a randomly generated minecraft world on the outside. The grey stone world would get a little boring after a while. Just a suggestion, I'm not a tech guy so I'm unaware a to wether what I just said is possible at all.
Sol