Theory: perhaps the letters do not have phonemic content?

[oshfdk]

Maybe it is. But in my opinion, you don't really understand what I want to convey. I'm not saying that this language is impossible, bad, etc. I'm saying that its creation and application is impractical.

Why should it be practical? If its topic turns out to be about summoning demons, divine revelations or plant magic rituals, the impracticality could be an essential part of the process. The harder and more complicated this is, the better.

In any case, whatever you consider practical is not necessarily what people who created the VMS would consider practical. Here is a recent example: You are not allowed to view links. Register or Login to view. that contains 400 PAGES of enciphered dictionary articles (for verbs only) from a know dictionary. Would you call this practical? 

If you still don't understand what I'm talking about, then I can suggest that you try to create your own language (manually!) and write a big book on it. The language should not be gibberish, it should be meaningful and readable. When you start doing this, you'll probably understand what I mean by complexity

I still don't understand what you are talking about and I'm certainly not going to spend my time on this exercise   As a counteroffer I suggest you try to create your own mysterious manuscript that would grab everybody's attention and then would resists all attempts of making sense of it for hundreds of years.