The transcription is just a planning tool for the committee itself, to guide its decisions. It is not supposed to be used directly by the speakers; IMO the orthography itself should be kept Latin-26, at most using one or two diacritics or new letters if necessary (see note*).
And the transcription should not be phonetic, for the “raw” sounds. If dealing with a single dialect, it would be phonemic, and deal with the abstract units of speech aka phonemes, since they’re the ones that you need to distinguish on first place.
And, since you’re dealing with multiple dialects, you need to reach a compromise between them. Then instead of a phonemic transcription, you go a step further, with a diaphonemic transcription. (Wikipedia has a rather good article on diaphonemes, but in a nutshell: they’re a compromise between the phonemes of multiple dialects.)
*note: if I were the one in charge (Bad Idea®), I’d probably consider the diaeresis; English has a lot of vowel phonemes but usually avoids vowel sequences, so it’s less intrusive to mark “this looks like a digraph, but it isn’t!” than to mark vowel quality itself.
The transcription is just a planning tool for the committee itself, to guide its decisions. It is not supposed to be used directly by the speakers; IMO the orthography itself should be kept Latin-26, at most using one or two diacritics or new letters if necessary (see note*).
And the transcription should not be phonetic, for the “raw” sounds. If dealing with a single dialect, it would be phonemic, and deal with the abstract units of speech aka phonemes, since they’re the ones that you need to distinguish on first place.
And, since you’re dealing with multiple dialects, you need to reach a compromise between them. Then instead of a phonemic transcription, you go a step further, with a diaphonemic transcription. (Wikipedia has a rather good article on diaphonemes, but in a nutshell: they’re a compromise between the phonemes of multiple dialects.)
*note: if I were the one in charge (Bad Idea®), I’d probably consider the diaeresis; English has a lot of vowel phonemes but usually avoids vowel sequences, so it’s less intrusive to mark “this looks like a digraph, but it isn’t!” than to mark vowel quality itself.