Before i go on I want you to be aware that the sum total of my current knowledge in Wing Chun stems entirely from my Sifu, any other knowledge that I have seen on wing chun, whether through articles, forums, videos etc, I view in the light of what my sifu has taught me, and I do not take anyones elses interpretation of Wing Chun on board. Now I may be close minded (or rather I may be labled as such) however i only do this because of who my Sifu and because of who he has trained under personally. Also being in his mid 60's he can kick my *** every which way. If you want to know more about my sifu yu will find a short thread on him here
To answer this properly let us examine the heart and soul of Wing Chun.
Wing Chun is a martial art is an art dedicated to the proper development of energy in relation to the use of the proper biomechanical frame. In laymans terms the concern of the Wing Chun practioner is to acheive body unity from the soles of your feet to the crown of your head, and how to utilise the proper centre of gravity so that your stance may serve as the foundation for power generation, stability, as well as the ability absorb and redirect the energy of the oponant (a common mistake that many people make is to assume redirection of force is achieved externally through the use of deflection and pivoting. This is [as my sifu would say] kindegarten stuff. True redirection of force happens internally through the stance). In other words the essential heart of Wing Chun is the stance, everything flows from the stance and has its foundation in it.
Now the reason why I am laboring this point? The arms are seperate from the stance, they exist with one function and one function alone,
structure which is why in the Sui Lum tao, every hand is to performed in a relaxed and soft manner, there is no forcing of the hands, the weight of gravity is to be felt on the arms, the shoulder is to rotate easily and smoothly. In fact in the Sui Lum Tao it is not so much the moving of the arms it is simply the changing of the position of the structure of the arms and how that is to be powered
by the stance. Structure contains no power of itself, it simply rests in something that is more powerful, like the arms of the Jong, they move yet have structure, but where does their strength flow from? From the pole, however the difference with us is that the pole moves and has an energy behind it. The goal of the Sui Lum Tao is to cultivate this energy which flows from the mind (little idea) and to learn how to utilise this energy through our stance to support the structure of our hands (arms).
So in relation to your question, the answer is simple, using wieghts to try and develop your wrist strength or any other type of strength in your arms is a futile practice in Wing Chun (now at this point many will disagree, I expect that) because our true power rests not in our arms but in our stance, in the execution of proper body mechanics, in harmony with the proper energy as has been (or should have been) cultivated through the Sui Lum Tao. Any muscular development (except that which occurs naturally through training) will actually counteract the cultivation of this proper energy, but not only its cultivation but out ability to utilise this energy when the time is needed.
In conclusion I will say this, if you want to develop your muscles then so be it, in the short term it may well enhance your development as a fighter, but it will (and I repeat it will) not might, retard your development as a WC fighter in the long term.