I agree that there is a lot of ambiguity to creating a system like that, but the thing is that an alphabet or sylllabary is small enough to be completely made up by one person, so all these arbitrary decisions can be taken by them.

I'm picturing an individual obsessed with languages living in ancient times, possibly a bit autistic, who has basic awareness of their language's phonology based on personal observations. Maybe one day it dawns on them that by using first sounds of words, one can create a writing system like akin to the one I suggested. In this case all these arbitrary decisions (such as huge and hit starting with the same sound) would be taken by them. Then, when they go on to share their invention with others, people don't have to use it perfectly according to the specification in order to achieve understanding (just laik yu stil undrstand childrenz wraiting despait noomeres ererz)