I just wanted to put this out there so that aspiring rune workers can learn from this bit. The blank rune holds no place in traditional rune work. It was never a stav that was considered to be worked with. So when you get a rune set online or from a store don't use the rune and don't discard it. Simply keep it in case one of your rune stones break.
The whole blank rune idea started largely with Ralph Blum. This author began selling his book with premade rune sets in the 80s. I have one of the original sets and the original book. I can honestly say that Blum's book is sound but it contains ideas that are not traditional and are largely New Age concepts pulled from cultures from various parts of the world.
If you do not value the tradition a whole lot then by all means use the blank rune. It's up to you, I can't force you not to. Just know that it really isn't a rune at all. Just a blank stone or piece of wood.
I don't doubt your right but not knowing much about runes and finding your post intriguing I looked up the definition of the term Wyrd. The term seemed familiar so I also wanted to discover why, though I have yet to. This site/link doesn't contradict your point but defines the word and rune meaning, though I'm sure you could find multiple definitions on the web. http://urbandictionary.com/#define?term=wyrd
Wyrd is just like fate. Deities called the Norns web together wyrd. So the authors who claim that this rune is to be compared to fate/wyrd/the unknowable, it's all bogus. It was never a real traditional rune of the Elder Futhark.
Here's a good explanation.
"You may have picked up a book about runes or purchased a rune set that includes a "blank rune", "Odin Rune" or "Wyrd Rune". This is a very strong clue that author is not an authority on runes. There is no historical evidence that runemasters of old ever used a blank rune. It's self-evident because a rune is a symbol, not the token that carries it. Have you ever seen a blank symbol? Of course not, that's an oxymoron."