As I've said elsewhere (other threads) over the years, I've done much of what you suggest.
Homebrewing classes and setting specific things is -in my estimation- one of the great joys of D&D/fantasy RPGing.
My "Arcane Magic" list is applicable, in it's entirety only to [what my game terms] the Mage class [I do not -in fact, all out refuse to- draw distinctions between "Wizard" and "Sorcerer," at a class level].
The "specialist" Mages, Illusionists, Conjurers, etc... have individualized spell lists that are (roughly) half spells that would be available to all Mages and half spells that are available only to the specialist. It's all still considered "Arcane" magic, because of the nature of the force with which they work. But in the class crunch AND the setting fluff, there is such a thing as "Phantasmal [or, simply, "Illusion"] Magic," "Conjuration Magic," and so on.
E.G. The any "generalist" Mage is going to be able to learn, e.g., Wall of Fog, Glamour (i.e. Disguise Self), Invisibility, Mirror Image, Phantasm I (i.e. Phantasmal Force). Illusionist spell lists have all of that stuff too, of course. But they will also have, e.g., Gaze Reflection, Dispel Illusions/Charms, Phantasmal Killer that general mage's don't. They get things like Phantasmal Force and See Invisibility a level earlier than general Mages...AND, the Illusion Magic Specialist would gain spells like "Phantasm II" and "Phantasm III" (ever increasingly powerful and convincing "Phantasmal Forces"), which the general Mage can never master.
So, I like the combination of common magics and specialty magics.
I also make a distinction between Divine and Nature magic, so Clerics and Druids really aren't working from the same "pool" as it were. So the handling/figuring out how best to do Cleric/Divine magic is really it's own individualized thing.
Druids (and other Nature Magic users) are fairly well tied into natural and elemental related spells and all draw from the same list...though individuals could certainly choose to focus all of their preparations in "plant stuff" or "weather stuff" or "animal and fire spells" or whatever the player likes. But I have not yet come to a place where "grouping/separating" magics for Nature magic-users is necessary (or has been requested).
In the Ashen Lands I have this idea of sources.
Arcane: The Within and the Without. Because Sorcerers were the first mortal spellcasters, magic from within is what most people think of as "Arcane Magic" and it comes from you. Magic from Without is Wizardry. Using the rules of reality to bend themselves through carefully manipulating reality with ritualized sounds, gestures, and physical representations.
I think all Arcane spells will be available to Sorcerers and Wizards, even the school "Specialty" spells. Kind of to represent the egalitarian nature of Arcane magic. If you have the birthright or the skill you can do it all... within your personal limits.
Divine: The Gods and the Angels. The Gods cover a variety of concepts and are generally pretty loose in their interpretations of magic. Angels are -much- more strict because they exist to protect Elysium (Heaven, basically). So they're all sorts of focused on Justice and Mercy.
A fairly robust central pillar of spells but then spells unique to the Angels and spells unique to Domains.
Occult: The Gone, The Mind, and The Beyond. The Beyond are Old Gods, but in a more directly Lovecraftian way of reality-warping rather than traditional "Spellcraft", so occult magic is representational. The Gone are people and concepts lost to the Occult or Time which provide a mortal structure to the magic of the Beyond that makes it "Safer" to use. And then the Mind is Psionics, because reality was formed by the Old Gods and their influence on all living beings is still present, there are those who can intuit and study how to use their will and ideas to alter the world the Old Gods dreamed into existence.
I'm thinking very narrow "Central Pillar" of Occult Magic and then a -whole lot- of specialized spellcasting for Psionicists, Warlocks, and Bards.
Primal: The Elements, The Green, The Wild, The Storm, and the Reaping. Green referring to Plants and the Old Court and Wild referring to Animals and the New Court.
Probably make The Green, the Wild, and the Storm central to Primal casting, then have the Elements and the Reaping more specialized, with some Wild/Green/Storm specialization, too, but to a much lower degree...
Interesting thoughts, thank you!
And that is a radical interpretation of what I said.
You were talking about the gods. I assume the gods of the setting to be NPCs. Not under the player characters' control. But I also assume them to be characters in their own right - and if they are characters in their own right and I zoom in enough of them they will start doing things I do not expect. There are things that individuals will not do because they are contrary to their nature. But if it's something they could do that wasn't suicidal and there's a reasonably large group of gods then I can assume that at least one of them will have tried it. And if I actually start to write the gods as people then some of them will behave in ways that are in line with their nature but that I don't expect.
Likewise if there's an age old enmity between the elves and the dwarves there will be friendships too. If the baseline setting is not ragged at the edges and fraying at the seams it's because the people that live there don't behave enough like people.
And this is why the presence but rarity of Divine Soul sorcerers is far from a worldbuilding issue if we have an entire pantheon. By denying them you're saying either (a) the Gods can't even manipulate the magic of a single mortal that way, which is a weird limit on their powers or (b) the Gods can but are so stultifyingly conformist that none of them would ever try. (This doesn't mean that divine soul sorcerers have to be remotely as common as clerics of course; there are dozens of reasons why one's rare and one isn't).
If your characters act in a manner you do not expect when you are writing the BACKGROUND of the world, not current events or the story as it progresses, but the things that have historically happened, then I am in awe of the chaotic nature of your writing style. Full on biblical -Awe-.
I've also stated I won't be arguing the specific loopholes of various concepts or what have you for a given idea or identity to exist in a setting. It's pointless and exists outside of the relevant discussion of writing the campaign setting to include class fantasy. Similarly, I won't be going into the discussion of which character groups will or won't be friends and whether that should be a global rule or a general guideline or something to be ignored entirely 'cause it's all setting and table dependent.
