Mrz
Your claim that
Children like Indigo's daughter would struggle no matter what orthographical system was used
is simply wrong, and blindingly so.
Countries with more regular orthographies have far fewer children with reading problems. They also all start the teaching of reading later, because they know that it does not take long and gives extremely few children problems.
The Rose review admitted that. So does the L&S guidance for teachers. It recommends that Phase Five should take about a year but also explains,
Phase Five would not be needed if there were a perfect one-to-one mapping between graphemes and phonemes. ... English is unlike most other languages, however, ... that is to say, most phonemes can be spelled in more than one way, and most graphemes can represent more than one phoneme.
There is no doubt whatsoever that fewer English-speaking children would struggle with learning to read and write if English spelling was more consistent.
U may, for example, be extremely attached to all the words which don't spell the short /e/ sound with e, but they undoubtedly help to make learning to read English harder than other orthographies:
Bread, breadth, breast, breath,
dead, deaf, dealt, death, dread, dreamt, head, health,
lead x2 [led/leed], leant, leapt, meant,
read x2 [red/reed], realm, spread, sweat, thread, threat, wealth.
Longer words with : Breakfast, cleanliness, cleanse, endeavour, feather, heather,
heaven, heavy, instead, leather, measure, stealthy, treacherous, treadmill, treasure, weather.
Friend. Leisure. Against, said, says, every, Wednesday.
The following are also without a doubled consonant after short /e/ (compare ?penny, teddy, jelly):
Any, many;
Already, jealous, meadow, peasant, pheasant, pleasant, ready, steady, weapon, zealous;
jeopardy, leopard; bury; heifer. (Masha Bell 2011)
Using for both the ee sound and short e is extremely silly and does nothing except make learning to read and write English harder. I don't pretend to be an expert on how best to enable children to cope with such a silly spelling system, but I do know which spellings make learning to read and write English much harder than need be, and much harder than all other European languages.