You know what, I'm kind of sick and tired of most magic fixes. So I thought of a simple one.
Spells are all magic items; price 'em as schema (those 1/day scrolls from Eberron) or something; you still have ability score prerequisites and such. However, casting spells is harsh on the mind, as such arcane forces were never intended for mere mortals; use something like this
In this kind of system, a spellcaster wouldn't inherently gain spells; they'd be all about better utilizing the spells they get (a Wizard would reduce Corruption, maybe get the ability to use low-level Schema more than once a day, and so on and so forth.)
Divine schemas would be made as Relics, and so would require the True Faith feat to use.