reading [y] as a null character

[-JKP-]

The problem with the idea of [y] as a general-purpose abbreviation symbol, standing for a wider variety of abbreviations, is that one could then make it represent almost any grammatical or derivational suffix one pleases, in any language. In this case the script would give us almost no information about the actual grammar of the language--the rest of each vord would presumably represent the roots or stems of the words, but as soon as each word reaches the grammatical suffix, we would find the identical [y]!...

It doesn't have to represent any kind of suffix. In languages that use Latin scribal abbreviations, a single abbreviation can represent 3 or 4 different endings. It can still be read. Maybe this can be stretched to 5 or 6 if the ones it represents are similar to the ones that are traditional.