I really don't see a problem with doing this. You would have to look at the manual about "targetting" to see if you could activate a script if the "targetting" condition is meet.
The animation would for anyone who has done animation, take a whooping 30 sec to make.
[EDIT]
The closest one I can currently find is "PLRINGUNSIGHT" but I think that is for the enemy targetting the player and not the other way around. Should still be pretty easy.
Heck, it would be pretty easy to make a script that once you kill all the enemies in the room, that the hostage can follow you out to a location. I don't see a problem with doing that.
-This...is my boomstick!