Heres the link to the document!
Advance casting! Its vancian casting but for 5e as an alternate class feature!
I've had this one cooking up for a good while. Like, a few months actually. I was on like, a long train ride, hit the inspiration to start writing this, conceptualized the whole thing and got blasting.
And then like, I got to the druid, couldn't think up a good way to implement it, said "eh ill sleep on it."
and then me sleeping on it took actual months, until I just hit the answer I wanted while taking a shower and here it is, finished not long after!
Im most proud of the title. Advance casting sure, because you choose your spells in advance, but also its advance casting, as in, vancian.
Im awful for doing that haha.
But yeah, balance wise, if you're a paladin, cleric, wizard, or druid (the prepared casters of 5e), you can choose to be an advance caster. From then on, you exclusively have vancian rules for your spellcasting, but in exchange, you get a few extra spell slots per day (Albeit, extra spell slots with limitations in what spells they can choose.)
So, the paladins bonus spell slots are exclusively for their oath spells, and the clerics for their divine domain. Wizards get to pick a spell school, and druids a "elemental force".
Notably, the cleric and paladins bonus spell slots can cast spontaneously with these bonus spell slots any of their oath/domain spells, the druid only gets one spell per level, but can freely upcast, and the wizard can prepare any spell they know into these spell slots (so long as its in the spell school) but their bonus spell slots work vancian style still.
So yeah, theres a distinctness to how these bonus spell slots work.
These bonus spell slots are very much inspired with Clerics in 3.X and their domains, and how they'd get domain slots for their domain spells. I think its neat.
Also an intresting thing, on the Cleric, Wizard, and Druid, you get to choose whether you want full progression with your bonus spell slots (1-8), or twin progression, (two sets of 1-5).
I think its nice because it lets you choose between pure strength or wide versatility. The twin progression paths arent as strong sure, but you get a lot more spells available at hand, and a couple more total spells per day.
The druid is kinda unique among these in that, my struggle with it was that it didn't have an equivilent to Domains, Oaths, or spell schools like the other classes, so that was what locked me out of finishing this for a bit
It actually was my last homebrew that drew me out of this lock, the Sha'ir, since it had a handful of 0-7/8 "planar revalation" lists exclusive to the class, and then I realized, "Wait, I could just use something like the planar revalation lists"
The planar revalation lists are actually pretty similiar, with the air/earth/fire/water ones being not 1:1, but the basis for what I put in for the druid. The Flora and Fauna were brand new. But yeah, thank you other homebrew for helping me finish this one.
Also, druids and clerics are unique here in that they have spontaneous magic still, though only a single spell.
Cleric choose at level 1 between Inflict Wound or Cure Wounds, and can from them on exchange any prepared spell or spell slot for their chosen wound related spell.
Druids on the other hand, get to pick between their circle spell list (if they have a circle spell list), or Goodberry / Entangle with bonus perks for upcasting them.