Could incantations explain some of the problems of the Voynich Manuscript

[oshfdk]

Newbie here, so I'm prepared to be shot down in flames, but aren't you falling into the trap of assuming EVA transliterations represent the actual sound of the Voynichese "words"? For example, in reality we have no idea which of the glyphs in EVA <aiin> are vowels or consonants, do we?

I think the argument goes something like this:
1) Voynichese shows repetition with variations because it's based on spells or chants
2) If so, it still can be a simple substitution cipher/custom script, and all the weird statistics belong to the underlying text itself
3) If it was simple substitution, then for most languages o/a/e would be natural candidates for vowels, it doesn't really matter which vowel is which

I'm not really buying this, because even in the example with the love charm above the chant part is only a small piece of a meaningful text, I don't think a whole book of illustrated chants/spells and no explanations makes any sense. What would you do with spells/chants if you don't even know which one is which? But who really knows these medieval folks.