Mandoble's code won't work -> in ArmA, it's entirely impossible to revive a dead entity in SP, AI or Player.
However, you CAN "Respawn" a player simply by using selectPlayer/adding a new unit to the switchableUnits array (and allow the player to pick their teamswitch in the death-menu).
something like:
this addeventhandler ["killed", {addSwitchableUnit RespawnDude; selectPlayer RespawnDude}]
You could of course just keep creating new units named "RespawnDude" as well to make sure the "killed" eventhandler always has someone to respawn into. Or use some script.
All is possible!
Good luck!
Wolfrug out.