Hello everyone...
I came up with this idea just out of nowhere.. Maybe someone made it already... But this is how I thought about it...

I put 1 layer of bedrock on the bottom of the level, then 5 layers of water above that,
and then above that, in the air, all players ( on a server ) can have their own Glass-ball...
each glassball will have an airstrip, and everyone can build their stuff in that ball.
Then there can be public balls, where shops etc. can be... and everyone has their own airplane...
I began with 1 island, And the pictures are above...

I'm using my own texturepack, which you can find by clicking my name (simple texturepack)