How multi-character substitution might explain the voynich’s strange entropy

[quimqu]

Interesting work!

A homophonic substitution cipher with positional restraints is basically the same thing as positional allography, right? So we would be looking for one glyph that's the equivalent of another glyph, and their positions tend to be mutually exclusive. 

I think this is an underexplored avenue that might solve a lot of our problems. But it creates new problems also. Let's say in practice, a medieval text may use something like 22 letters frequently (we can do without w, u/v, j...). To enable homophonic substitution, the number of frequently used characters needs to increase. So you would end up with something like Arabic with 40+ letterforms. 

However, if the 20 something frequent glyphs of CUVA are our expanded set, then that means that solving the homophonic part of the cipher would mean a drastic decrease of the number of letters. To accommodate for that, you would need a cipher that's polyphonic and homophonic at the same time. (Which might not even be as  impractical as it sounds).

Not really... I tried to explain that in my last answer. We can use the same number of characters. For example:

a can be ciphered by (T,O,P)
b can be ciphered by (U,P,W)
c can be ciphered by (T,M,Z)
...

As you can see the voynich characters (represented by the CAPS) can substitute up to 3 natural language characters. But this is tricky to decipher. There should be another hidden rule to  know when to cipher with one of the three characters, and this rule may not be very obvious. I have already done some experiments with the appearance of the characters. For example the word "appear", I culd change the first "a" by char #1 and then the second "a" by char #2 etc, etc.. But this gives more understansabilty to the cipher and then the entropy bump dissapears.

So yes, in my opinion there is a hiddn rule. And we even don't know if there are 2, 3, 4 voynich characters to cipher.