That's right. However, some letters are silent, or words are homophones, in all accents of Standard English: rite, write, right, wright could all be spelt rit

That's right. However, some letters are silent, or words are homophones, in all accents of Standard English: rite, write, right, wright could all be spelt rite (and disambiguated by context); the k could be dropped from knight, knave, and knee; the 'b' from debt, doubt, and subtle, and the 'l' from could, should, and would. These changes would work for all accents. There are probably several hundred words whose spelling could be reformed.