Let alone "absent in some varieties", there are sounds that are absent in all varieties but still spelled (e.g. the h in hombre or the u in queso). There was an attempt to regularize that in Latin America but the countries that tried to adopt it reverted back to the old spelling[1] - I guess the same will happen if someone tries to "reform" English
[1] https://en.wikipedia.org/wiki/Bello_orthography