I have just started Development on that Project don't expect this to be out soon!
I will be trying to Create a server mod, that allows the chunks or predefined area to be visible to some people and normal flat land to others. Creating a stable base like this makes thousands of other cool stuff possible, You can define if a certain player group (Permission Integration) can see a block or not, optionally they can also walk through the block. After thinking a while i might believe it is possible (just as a wrapper) that different Minecraft versions could connect to the same server, i will possibly create a small wrapper that lets the versions through different tunnels in different sections of the Server. Its complicated thats about as simple as i can get!
I will post pictures When i get further please leave comments, tips and suggestions in the comment box!