It is unfortunate that this sort of mathematics wasn't available to the students who were creating the Euler font.
https://tug.org/pubs/annals-18-19/euler-summary.pdf
Another consideration which I'm surprised wasn't made use of is that letter recognition is overwhelmingly focused on the upper half of letters --- ages ago, there was a typeface developed which took advantage of that, providing variants of letters where the lower halves were modified so as to indicate how a particular letter used in a particular word was pronounced, so that the "c" in "cat" had a different lower portion from the "c" in "cent".
That said, I'd really like it if they would publish the software used to make this font, ideally as opensource --- I have a type design project which stalled against the need to create variants for each size, working from an incompleat set of letterforms at each size (the only letters available in the compleat size range from the sample I had were "n" and "N", go figure) --- I believe this would let me finish up all the sizes of the design.
Initial Teaching Alphabet perhaps? - a bit more radical than what you are describing though.
https://en.wikipedia.org/wiki/Initial_Teaching_Alphabet
As the 'pedia page says, the main issue was transfer to mainstream letters. I came through infant school a year or two after this idea was abandoned in the UK. We did have the colour coded reading books mentioned though.
No, that's not it.
I suspect that it was a personal project of some teacher at some school I was attending, or maybe it's something which I came across while studying typography which was never actually implemented.
Anyway, I think it's an idea which someone should give a try --- maybe I will some day in a future font design.