I haven't meddled with camera controls myself yet, but I presume this would work:
mission_cam_set_target_agent = 2017 # (mission_cam_set_target_agent, <agent_id>, <value>) #if value = 0 then do not use agent's rotation, else use agent's rotation
Say, spawning the off-map agent, set player to control that agent, possibly kill that agent(Got to disable the player from respawning if it's like deathmatch or so though when choosing to kill the agent) or not, and then setting the mission_cam_set_target to the original agent until it's either dead or until it's morale is back up, in which case it can be controlled again. (Or the player can respawn incase it died)