I will still argue that *part* of the equation is the body's own defense mechanism. The back muscles and back of the shoulder must stop the punch and your body is smart enough not to throw a punch faster than your body can stop it. Otherwise, you'd rip your arm out of the socket. Training for baseball pitchers is the same way. It's kind of like not being able to lift as heavy with dumbbells as you can with a barbell. The stabilizers have harder work with the dumbbells and the body will shut down the prime movers if the weight isn't stabilized. Further, the backs of boxer's are built because of all the ballistic loading from stopping the punch which isn't just an arm, but also the gloves and raps. The ballistic loading of kips would mimic this and be helpful in my opinion.
Certainly the ability to put your body behind it (i.e generating power from the hips etc)is very important. As Dan John says, "the body is one piece." (I think it was him who said it).