the trigger has an area already. all objects which fullfill the triggers condition to activate will be in triggers thisList array variable.
The only thing u ve to do is to execute addCamShake for all players in those thisList in triggers "On Activation"-field and do the same thing with resetCamShake in triggers "On Deactivation"-field.
I will implement "START=" in the next version of JEBUS because I can see your point about server lag when multiple groups spawn at once.
I was hoping the next version would involve a comprehensive clean up of the code and implement some new features, but I may just make a quick release for now and work on more ambitious things when I have more time.