[pjc50]

The thing is that English takes in words from other languages and keeps doing so, which means that there are several phonetic systems in use already. It's just that they use the same alphabet so you can't tell which one applies to which word.

There are occasional mixed horrors like "ptarmigan", which is a Gaelic word which was Romanized using Greek phonology, so it has the same silent p as "pterodactyl".

There's no academy of the English language anyway, so there's nobody to make such a change. And as others have said, the accent variation is pretty huge.