The thing about the forms in wing chun what you see isn't necesarily what you get, for instance when you look at the first form you aren't presented with moves as they are used in application, you are given a conceptual idea on which to further build and understand. Just seeing where to put your arms on a dummy won't give you the understanding of what its teaching. You'll need explanations of the ways these moves arise, how to employ them, what energy feeds them and what energy is used to make them effective, how to hold structure and a lot of other stuff that begins being taught from day one.
If you want to learn basic things from wing chun i would suggest first studying the strarting point - sui lim tao, otherwise anything you gain from wing chun will just be swiss cheese. I'm not trying to say don't bother learning it but to get any worth out of what the dummy is teaching you in wing chun terms really does require you understanding the little ideas and nuances behind the shapes, energys and structures.
The other truth is its generally better to be an average joe of the street when begining to learn wing chun concepts and principles as they are very likely going to condradict the principles of TKD. Which is fine as you can still cherry pick parts of the system to suit you but you have to be aware that it would not be working as intended if the core priciples are dicarded, what you would get wouldn't be the wing chun dummy form even if it looked the same and how you applied it would also probably be very different. What you'd essentially be doing then is trying to bend your TKD ideas to act like something they aren't and i feel you'd be better off just treating the dummy as more of a blank canvas for you work ideas of TKD on.
There is nothing to stop you using a dummy and to incorperate it into your tkd training, in fact it can be a very useful training tool even when you remove the ideas of wing chun. So thats why i asked why learn wing chun and why that form, wing chun is heavily based on concepts and principles and if you want to use the shapes like hi-lo gann sau or kwan sau in a TKD manner then thats fine but the starting point of those techniques begins in sui lim tao and if you skip that part of the training you just have something that is perhaps aesthetically like a kwan sau but doesn't act like one.
I hope thats explained things and not sounded like i was trying to simply say you can't do it, i am simply giving an insight into why i don't think you would gain extensively from it and as dummys aren't cheap it would be a shame to waste the money. I know people, JKD mainly, who use dummies in a non wing chun manner and on a few occasions i've seen them become nothing more than a place to hang a coat as there turned out to be no use for it for them. Just food for thought really, good luck in your decision.
