Was discussing this idea with the other players present (two were missing, but I digress), and this seems like an idea that would work, but I have the feeling we missed something.
Instead of banning the prepcasters like I was thinking, why not just lift the appropriate 6 or 9 level spells/day and spells known charts from the spontaneous casters and apply it to the Cleric/Wizard/Druid/Magus/etc? The individual class features, with some exceptions of course, would remain the same.
Outside of the Wizard/Magus spellbook (which would just not be a thing), I can't think of too many class features that would need adjusting. The cleric domain spells would simply be additional spells known (same with domain druids) ... any other abilities I'm overlooking?
Interesting idea, a couple thoughts: SNA would be added to druid's known list, and bonded items for wizards get a big nerd in this.
Would domain and specialist wizard slots be required to be used for the appropriate spells?
Wizards getting scribe scroll for free is less useful now.
Re:
SNA Druid - True, easily done.
Bonded items - True. Might steal from the Vanguard class and let the staff replace somatic components for spells, or remove that concentration-check-if-you-lose-it deal.
Scribe Scroll - Good point. Can't recall the last time I saw anybody use it, but good point. Easily replaced with a bonus feat, or go the PFS route and make it Spell Focus. intending to make magic items less of a thing in this game, anyway.
Specialist wizards I hadn't thought about, thanks for mentioning that. Give them one extra spell known per level, must be specialty? Works for clerics, too ... two domains, pick one domain spell at each level to be a bonus spell.
Kind of mirrors the Sorcerer/Oracle bloodline/mystery thing ... yeah, I like that.