How to seperate sublevels for different clients

Hi,

I wish to make one overview map which allows me to hold all (maybe 20) players on one server. Some features are singleplayer mode with a indirect effect on the overview map, no one except for the player who ownes the singleplayer area can see what is inside. Sounds like i should load a sublevel with ‘only relevant to owner replication’ mechanics inside. But serverside that level would be crowded from stuff build by the players and I can not differ from which is whoms stuff. So the game mechanics would recognize false information on the servers side. My Idea is to arrange the Level in slots for each player, seperate in location. So one player build between 0-5000 x,y,z and the next one builds his stuff 5000-10000 x,y,z. But maybe there is a better solution out there.

Thanks in advance,
Maxx