There's never any issue in cosplaying, and I find it interesting that they tried to put it on a TV show. My only objection is that it looks atrocious. From a fashion perspective, the clothing does not suit Ya Hui's figure at all (the shirt makes her torso too long without outlining anything, possibly because it's badly cut, the pants and boots were a terrible choice), and given it's a TV show, I'm sure they had the budge to fix it up a bit and make it at least look better on her. Sorry if this sounds like nitpicking but when people dress well it makes me happy... >_< Ya Hui is clearly as beautiful as everyone is, and yet the outfit they chose for her makes her look silly and bad. The shorter wig
could have worked but it doesn't; the hairstyle is not even "modernist", it doesn't work for her face shape.
The girl wearing the sakura outfit, on the other hand, looks much better. I guess it's clearer when you look at this
photo that they put in the article; look at their image in the small screen. The ladies seem to be about the same size so you see that the fault is on the clothing, not on anything else. Yes, the shirt in Miku's original design
is long, but it's not a long that looks bad on the person's body - it's a long that looks harmonious. Great clothing makes a person's figure look harmonious, it's all about playing out their best features. Colours, cuts and shapes make all the difference in presentation. Compare the pants and boots for the sakura lady and then compare their choices for the Miku lady, and how one complements the rest of the outfit and the other doesn't.
Tl;dr they look silly because they were made to look silly. Even their overly vibrant lipsticks could have worked if they had bothered to give them better clothing. That would have been a better presentation of something with such a big fanbase such as VOCALOID. I'm not sure what their purpose was, but they could have done it better.
(On a separate note, I'm impressed that Mothership's article summed up this aspect so well:
"While the voice in the software was provided for by a real voice actress, Miku’s image provides an identity to the voicebank." That's some great wording ^^)