Hm. It sounds like creating plushies could be a challenge.
It does look like there is more interest in chibi plushies.
Now, this does help. From what I observe, chibi plushies could allow for some details to be omitted. Besides, a super-chibi plush is possible (one with very little detail, a simple face, etc.), especially if at a smaller size.
I own some Miku plushies myself, and from what I see, the floating ponytail looks fine. It's not actually floating (that would be cool though), but it works well to still make for a great product.
Now, I wonder if something
related to a Vocaloid is possible for a plush. Such as Miku's signature negi/leek or Fukase's "Point" character. It will not be the same as an actual Vocaloid character, but this does save fabric and possible time.
I at least discuss it as it could be a good starting point for learning more about sewing. It's not a focus, but I wonder if such items as these there is interest in? If I am to sew, this may be where I would need to start. Simple, then grow to more complex designs/patterns.
For example, if I were to sew a Fukase

, I may give him a simple white coat without some details on the coat. It certainly would not be the same as a plushie that has all of these details, but for sake of starting out, I do not think I would add them.
So, I think there are ways to get around these factors, it will just mean some parts will be taken away from the true design. In the end it will be balancing quality and resources.
How true to the design do you guys feel merchandise should be?
For me personally, I find myself enjoying an artist's own interpretation of a character, meaning some parts of the design will be altered (such as height changes, hair size, etc.). So, I suppose one could phrase it as, I enjoy some similarities to the design, but it does not need every detail or part, or to be a match.
Also, sorry I am asking a lot of questions. These discussions are bringing up some good points I think it would be good to point out. I have been considering using Google Docs to make the next poll, and might put the design-related question in as well.