These are nice features.
There are some words in English that are spelled with consonants as the first letter but when spoken are pronounced with a vowel, likewise sometimes they are spelled with a vowel and pronounced with a consonant.
For instance;
hour, honest, honor should all be 'an'
unit, user, utility should all be 'a'
I'd be lying if I said I knew them all (and given country and regional differences there are likely exceptions within the exceptions), but perhaps functionality could be added for these exceptions and users could submit them as they're found.
As a start, this page has vowels pronounced as consonants.
https://www.wordexample.com/list/words-beginning-vowel-no-an, I was unable to find a similar one with vowels.
There was also this stackoverflow question, and one guy downloaded wikipedia to come up with a javascript function.
https://stackoverflow.com/questions...y-prefix-a-word-with-a-and-an/1288473#1288473