How do you know it is possible? And more important what do you need it for? Is your mission so damn hard that you'll need respawn - in sp?
Give the player the chance to save the game, that's perfectly enough, even for hard missions.
Player must be the squad leader or work alone, make a trigger, radio juliet (0-0-0 in the radio menu). Condition this, OnActivation savegame.
UnPBO some missions (BAS missions by Nagual e.g.) to see what i mean.