Summary
This would be a simple way to let 16 people all play the same game, without the other person's interaction.
Brainstorming Ideas
You could, on client loading, create a full client-side copy of the bricks, which could not interact with the other client-side bricks
It may be possible to make all reactions, effects, fakekilling bricks, projectiles, player-objects, ect client side, and not the bricks
Uses
Portal maps
ZAPT singleplayer using online maps
FPS campaign mode using dedicated servers
ect