I do like the idea of treating spell levels as the quanta of magic, though. The spell-slots-by-level chart always reminded me of electron energy-level charts for various compounds.

That's why I like the slots for some classes like the wizard where your power comes from intense study. The slots make it sound like you've taught yourself to control your powers and make sure nothing gets wasted due to there not being enough mana or whatever left for any other spells. Same for things like clerics where you get your powers from your god, where the god is just saying "you get 2 3rd level spells today, nothing more, until you can prove you can handle it" or something.

But some classes like the sorcerer just feels. . . wrong. You probably don't even understand your powers, how can you understand something as ambiguous as a "spell level" if you didn't even learn magic. I feel like sorcerers should always just use mana instead (and if they want to keep metamagic as using sorcery points, combine them so we only have one resource pool to keep track of).