Let us say you play 8 BLUFOR troops on the ground. You have 2 choices, your the disableAI command to disable AI by default, or manually disable them yourself.
Next...well that is it. If you don't set up a respawn point, then everyone who connects will be dead and everyone that dies will stay dead. What they are not realizing is that the respawn feature has been in these games since OFP. What ArmA did was allow players to enter the server AFTER the mission has started. Hence the name Join in Progress. So, to sum up:
Add to the description.ext: disableAI = 1
Don't add Respawn_xxxSidexxx markers.
Or just make a mission and do nothing, there is no default respawn. By default, there is NO respawn.