Warlock
A half caster that uses the arcane list
Ranger
A half caster that uses the primal list
Paladin
A half caster that uses the divine list
Bard
A half caster that uses the arcane list, the primal list, and the divine list
Artificer
A half caster that uses the arcane list
It's not 3 spell lists and 3 half casters. It's 3 spell lists and 4-5 half casters.
Ok, I see where you are going now. Thanks!
First, although Artificer is now an official class, we will never use it at the table I play at so I am not concerned about it. Hate the class. Sorry.
Second, there will always be
some sameyness because of the fact you only have three, umm... aspects (?) of magic, but 8 different classes (9 if you include Artificer) and a couple subclasses that need to use those lists in some fashion.
My decision to differentiate them was to use the half-caster mold since it is already part of the game.
For myself, I don't want to further breakdown the lists by school/sphere/whatever you want to call it and then try to pigeonhole every non-Big-3-class into a series of restrictions. Limiting them to 5th level is an easier and still effective way to separate them from full-casters.
All that being said, you
could rewrite Paladin and Rangers so they have spell-like features instead of "spells", and do the same with other caster-classes as well, ultimately keeping only 3 casting classes based on the three aspects of magic. That is overkill IMO and not worth the hassle. Why? Because other than the three main casters (Cleric, Druid, and Wizard), the others have features that make them seem different to me so doing too much more in unnecessary.
Since that obviously isn't true for you, and you want to do more, I'm more than willing to lend a hand and try to help you get to a resolution you are happy with as well. For me, I'm pretty much there right now--I just have a bit more work to do.
So, as I see it, your issue at present is what to do with the Bard and Artificer...