I don't think hit points are the problem. Or, rather, I don't think hit points are my problem. My problem is the tonal shift, mechanically, from heroic to superheroic throughout the editions so that with 5e even low level characters represent a kind of flashy, over the top fantasy. That's not inherently bad. Sometimes I want that (the current Avernus campaign i am running is all in on heavy metal fantasy). But i have found it is really hard to remove that tone in 5e because the game no longer waits until 7th or 9th level to get super powered. Hit points and healing contribute to that, of course, but applying slow natural healing doesn't change the fact that the bard can cast cloud of daggers or that the barbarian summons ghostly ancestors or whatever. Changing that requires an Adventures in Middle Earth level overhaul, at which point the thesis of the thread -- how to get the game I want with a few house rules -- proves untenable.
I just mean hit points overall. Nothing says superhero more than people taking hit after hit of what would otherwise lethal or at least crippling blows, and gritting their teeth and pressing on.
Sure, if HP are narrated as luck and close calls and so on, that can address the issue somewhat, but it still leaves the fundamental problem: most individual attacks made on the PCs are not dangerous.
If you ditch HP altogether and moved to a more status based system, that problem totally disappears. However, doing that for D&D is far from easy because everything is set up with HP as the espectation; bad guys, spells, magic items, and so on all function accordingly.
That’s a lot to have to change.
This is why I’d try and incorporate Hit Dice in a more meaningful way, and leave the HP system largely intact. You’d still have to tweak some things a bit, but it would all be about HD rather than a fundamental change as far reaching as HP.
As for the spells and such....I mean, what’s the difference with a bard casting cloud of daggers compared to a wizard? That’s a sincere question. I can understand removing the magical subclasses for otherwise martial classes....eldritch knights and the like....but if wizards are available unchanged, then I don’t see why you’d bother removing the bard or sorcerer.
Another sincere question....how does AiME not fit your thesis? They took 5E and altered it to get what they want....lower magic, more hazardous travel in a dangerous wilderness, etc. Isn’t this, or something very like it, your goal?