Syllabification

[Anton]

This is a verbose cipher... every instance of the same plaintext word would yield the same sequence of ciphertext words

Not exactly - note that in my example "oolooooo" can be reduced to "oola" (as I did), but also to "alooooo". Which would be two different ciphertext words conveying the same underlay character (i.e., space). If we use this trick not only for "o" sequences, but also for "l" sequences, introducing a fourth letter into the alphabet, the degree of variability will rise further.

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Basically, what makes the ciphertext "unpronounceable" is the comparatively low number of letters signifying vowels in the alphabet as related to consonants. I think that if one uses an alphabet with roughly the same number of vowels and consonants, any ciphertext will be more or less "pronounceable".

Another cipher technique for making the unpronounceable ciphertext pronounceable would be just filling in "filler-vowels" according to a pre-defined pattern.

Yet another technique would be separately enciphering consonants and vowels of the plain text. I think that's the trick that would make any ciphertext pronounceable. Consider an example which is neither substitution, nor verbose. Don't know if it is a known cipher, but I just borrow it from the differential encoding used in the telecom world. Here, each subsequent character is not enciphered per se, but what is enciphered is rather the difference between it and the preceding character. E.g., the English alphabet runs: A, B, C, D etc. Let's assume we encode each line from scratch and the first word of the line is the word "odd". "O" is the first character of the line. It is enciphered just by its number in the alphabet - i.e., "15". The second letter is "D", which is 16 letters forward from "O" ("O" being counted itself). Thus "D" is enciphered with number "16". The third letter "D" is one letter distant from the second letter "D" (because we count the letter itself), hence it is coded with "1". We could well measure the distance beginning with 0, not with 1, but beginning with 1 is convenient for subsequent mapping of numbers to cipherext letters. In our example, 15 is "O" in the English alphabet, 16 is P, and 1 is A. So we get "OPA" as the ciphertext for "ODD".

Applied to the whole alphabet, such ciphertext would be unpronounceable for long phrases. What would make it pronounceable is considering two numbered rows - one for consonants (B, C, D, F...), another for vowels (A, E, I, O...) and enciphering consonants of the plain text with the first row and vowels of the plain text with the second row, using the same differential encoding as explained above. This way the phrase "this is a cipher", if I made no mistake, will be represented as "TNIM AB U KINSYL", which is quite pronounceable.