Insisting on using random Morse Code characters does not reflect accurately how Morse Code is actually used. It may well make the learning process more challenging and difficult but I don't know what possible real advantage there may be. I am also aware that all sorts of theoretical advantages are used almost universally by Morse Code beginners to try to make learning somehow "better." To my mind learning something in a comfortable fashion is much preferable to some evanescent promise of instant high skill achievement.
Most Morse messages are, and always have been, to a large extent predictable. We use, more or less, standard message formats. This provides critical context so that one, with a little experience, can relax with the assurance that what is to come next will be expectable. First your call sign, then "de" and last their call sign and a go ahead.
Making life simple is the way to move forward. Make it more difficult than it needs to be may satisfy masochistic desires, but I don't go there.