This is an attempt to consolidate all my feelings about D&D magic into a coherent system. It only concerns Wizards for now.
1. Wizards never gain new spells automatically. Spells are either found (as treasure), quested for (as player-set objective) or researched (during downtime).
2. Wizards receive a number of Spell Slots equal to their Int modifier plus their Wizard level. Two or more Slots can be combined to hold more powerful spells. The Wizard must always have more lesser slots than greater slots, this represents the time and effort invested into mastering the more powerful spells.
(example: Hanouk the Fabulous has an Int of +3 and is a fifth level Wizard, so he received 8 spell slots. He can have two level two slots (2x2) and four level one slots (4x1). Come sixth level he can get a third level two slot, and at seventh he can upgrade one of those into a third level slot)
3. A wizard can cast spells from her spellbook at any time, without memorization or anything of the like. Casting spells takes minutes however - each spell is essentially a mini-ritual. A Wizard can memorize a spell by pre-casting it and storing its syllables into his available spell slots.This allows him to cast (or rather release) the spell instantly, but only provided he performed the ritual at some prior time.
4. Cantraps (or cantrips) are minor, easy spells that almost anyone can cast with the right gesture and some words.
5. A final source of "magic" are the services of bound demons and spirits, which always carry a price.
I expect questing for and researching spells would be almost indistinguishable in practice. Both should be a challenge, produced by the "savvyhead" method + 2 or more choices. If the player says "I want to learn to speak to the dead." then the answer is "Yes, sure, but you'll have to...steal the secret from the necromancers of Thol Gharad or summon a ghost and try to learn from it or, heck, you could try and recover the lost Skull Mask of Firiandaur."
Finding random spells should follow the "whatever you think is cool" mantra for the GM + (random) treasure placement.
I would expect most spells to consist of purely verbal descriptions, with only minimal crunch where necessary. I honestly believe most spells could work with just one or two lines of description the rest is usually legalese to prevent rules lawyering, needless cruft. For example a spell could read: "With a touch you restore a living creature's energy, healing it by half its level worth of its hit dice, up to its maximum." Do we really need more? It annoys me when I read the spell lists in books or on the Pathfinder SRD, and the description says one thing but you always have to go double-check the actual spell, because the actual useful info is missing in the description.
I believe the above achieves several things:
-It makes magic a little more magical, by making spells something to be discovered, rather than picked off a list. It also makes it a bit more mysterious, and sometimes unpredictable or dangerous (as in the case of demons)
-It strikes closer to the actual vancian magic where one of the moderately powerful wizards we meet in the books could "memorize several of the lower spells or one of the more powerful ones". It makes different levels of spells more significant, as it would take a level 20 wizard to be able to cast a level 4 spell (of course this would make any old spell list useless - something the game wouldn't actually require any more imo*)
-It removes the need for the "15 minute adventuring day", at least for the wizard. No more adventures where you throw all your spells and then go to sleep for 8 hours. The wizard can cast spells at any time from his book (which takes a bit of time) and he only needs a short break of 10 minutes or so to memorize the spells for the next fight (casting from a book during combat is not optimal).
Am I missing anything?
*Lamentations of the Flame Princess completely discarded any sort of monster listing in what was a much lauded move. However it retained the D&D spell lists almost in its entirety, which to me is weird by comparison. The spells are refluffed to be more weird/horrible, but in a game where magic is supposed to be anti-scientific, chaotic, weird, with non-repeatable results a standardized spell list is just...odd. James goes to great lengths to make it feel different, but it doesn't really happen, both mechanically and from a seed content point of view.