But I would think (and remember reading somewhere) that phonetics shift more quickly where there is no written record of the pronunciation. Chinese has dozens of mutually unintelligible dialects (Mandarin, Wu, Cantonese, Hakka, etc.). Maybe this fragmentation would be much less if they had a phonetic writing system in the first place.
> In a few decennies any spoken language has shifted, vocalisation is different, especially when the language is used by loosely coulped communities. And then you have to adapt spelling to new pronunciations. But what do you do with old books? And how do you keep the language united?
English (or Spanish, etc) is a real-world example of a mostly phonetic writing system, and I don't think it is that bad. We can still read old texts, even though our pronunciation of the words has changed vastly. If you go back far enough (e.g. to the time of Chaucer in the 1300s), it becomes hard to understand what is being said, but practically speaking I don't see this as a big problem. In contrast, I think it's very important to have a writing system that is easily learned, so that it is accessible to the entire population (not just those able to invest lots of time & effort).