1.) Create respawn markers "respawn_..." for all four factions.
2.) Put this into the Description.ext:
respawn = BASE;
respawnDialog = 1;
respawnDelay = 5;
respawnButton = 0;
3.) Don't put any respawn templates into the Description.ext (haven't tried it with such).
4.) Run the mission in Multiplayer, join the server and open the game menu (ESC).