well for example a level with 10 players on it...
player 1 is in dimension/instance/phasingzone 2
player 2 is in dimension/instance/phasingzone 3
player 3 is in dimension/instance/phasingzone 2
player 4 is in dimension/instance/phasingzone 5
player 5 is in dimension/instance/phasingzone 6
player 6 is in dimension/instance/phasingzone 6
player 7 is in dimension/instance/phasingzone 5
player 8 is in dimension/instance/phasingzone 1
player 9 is in dimension/instance/phasingzone 2
player 10 is in dimension/instance/phasingzone 4
But only Players in the same dimension/instance recieve datas or can see each other
for example
Player 1 + 3 + 9 are in the same instance and they can only see themselves
Player 4 + 7 are in the same instance and they can only see themselves
Player 5 + 6 are in the same instance and they can only see themselves
and Player 2 + 8 + 10 are in different instances with different dimension numbers so they would see the level if it would be empty and if there wouldn't be any players at the level
The Game "World of Warcraft" uses this System for their "Phasing Zones" and theire "Player Instances" (Dungeons where every Group is in another Instance of the Level)
(For the ones who still dont understand what im talking about)
@Mark Sir Link
Just a full level copy is what I want to avoid - well then I think I must pick the long script alternative with a full custom System
Lets say the huge gmap would be a Phasing Zone - ouch a gmap copy for every player at the same time
Edit:
- hmm I think it could be worth a stress test try

well brb letting the server copy 100/250/500 levels at once and telling you what happened xD -
Edit: Result
100-250:
needed 5 seconds - couldn't figure out how much the server slowed down :o
but I can't test test more:
"Flood Alert: The script commands addguildmember,copylevel etc were called too often, fix the scripts please"
returned in the RC chat and now I can't use that command anymore o.O
well even a "/global servercontrol restart" doesnt work anymore: "Attempt to restart developer97: Error" O.O
Edit:
15 mins later:
The "copylevel" command works again but seriously I still cant use "/global servercontrol restart" anymore
1000:
Hmm a huge freeze for ~10 seconds but it works =)
Well finaly this is a possible way - and works very well
But I still prefer a scripting alternative