I'm not a linguist but it seems that most phonemes exist as areas (or multiple discontinuous areas as seen in TFA) in phonetic space while IPA attempts to describe only points in phonetic space[0]. Wouldn't it be better to instead just define X = {(F1min,F2min,...),(F1max,F2max,...)} for every dialect instead of making a universal X = (F1,F2,...) and then using it describe any area in phonetic space that happens to contain it?
[0] https://sail.usc.edu/~lgoldste/General_Phonetics/Source_Filt...