It can’t be done, in my opinion. You’re talking about trying to respell spoken language. But we have to take into account how much of speech is about trying to pronounce written language. I’m not talking about how it came to be. I’m talking about how it exists now.
First, there are so many accents and dialects, which one rules and becomes the standard? And how much of one’s native language becomes unintelligible if one’s way of speech is suddenly outlawed? It would persist underground, let’s not think it wouldn’t. Language is, if anything, more sacred and politically fraught than religion.
Second, a huge amount of meaning is in the word’s orthography (spelling), which is like its face and its biography both. A good deal more is in the context. Faced with the sound /ðer/ all by itself, how do we know what word it is? There? Their? They’re? That would be like putting a mask on the language and expecting us to guess. We’d be better off with kanji.
Phonetic spelling without a standard such as IPA would be completely useless. What good is it to say ”oo as in root” unless you know how I say “root”? There’s no natural way to spell a lot of sounds in English. How would you spell the sound of “cat” if it didn’t have the final t?
In speech, of course, we can clarify ambiguities by further discussion: “I meant ‘you’ plural when I asked if you were going with me.” In writing, we simply lose meaning.
In the end, I don’t think ambiguity in speech is nearly as serious as the risk of ambiguity in written matter. Our language would become a complete hash if we tried to adopt phonetics in place of orthography. Spelling modifications do come about over time, and I think that’s enough. Hardly anyone writes “catalogue” any more.
I took a Japanese class for a while when working for a Japanese-owned company. About half the students in the class were of Chinese origin. One day the Japanese-native instructor ran into trouble trying to explain a concept in English. Finally she went to the board and wrote a kanji character. All the Chinese members of the class went “Oh!” That’s communication .