Also, what objectives could an assassin possibly have besides kill...
Stupid, stupid idea...
What makes a kill objective any different than the medics revive objective? He's trying to move an NPC across the map, and an assassin isn't going to let him. A theft an objective countered with an elimination objective.
Again, I don't think they need a class for it, because the class is just a collection of tools to create a specific character anyways, but I see the usefullness in the role. After all, what is a counter operative if not an Assassin?