I see your point.. Tough we do not know how thick those blades and joints are.. I mean, the artwork is not that trustworthy when it comes to determining these things.. There seems to be plenty of room in the blade sockets on the arm, if those joints and the blades are as flimsy as they seem to be, your arm blades can prove to be useless if your assassination target is wearing any kind of armor.. (Your blades can even get stuck on the target, that can cause your blade to break from the joint.) Also, i just noticed that the joints appear to be ticker in the trailers, still not sure about the blades though..
Still, i think you are right.. They probably designed as a assassination tool, that says something about the girl on the trailer.. (She is either an assassin, or she uses them to kill her own enemies..)