How much work to write an enciphered manuscript v one with complex meaningless text?

[Mark Knowles]

I think the only way to find out is to try it. Otherwise it's pure speculation.

What we do know is that the VM would be a relatively massive ciphertext, so any increase in complexity would lead to a large increase in effort, if it is to be sustained throughout the whole text.

I agree it is very much a speculative question. I just doubt that there would have necessarily been more work involved with producing a manuscript like the Voynich using a simple substitution cipher copying from an existing text than producing complexly structured nonsense text of the kind found in the Voynich.