I wasn't sure where to put this... I spent some time reading Magic of Incarnum, which is very dippable and does a lot to fix non-casters, really, even if it's rather glowy. MoI + Psionics = Exalted, is the vibe I'm getting. Especially, if one also dips a bit into Tome of Battle. But that's not the topic here.
Every alternate experimental system WotC tried,
Tome of Battle
Tome of Magic
had a bunch of feats you could use to try out some of the features from the book. ToB had half level = IL + martial study, martial stance. MoI had opening chakras and incarnum feats. Tome of Magic had Bind Vestige.
Now, imagine if originally, there hadn't been a magic system - or had been an entirely different magic system - included in the core book set, and Vancian magic had just been released as a splatbook, and it had been written by competent people. All the spells would be there, and there'd be levels, and spell slots and so forth...
But, what would the classes have been? And what rules would they have included in the book? And what feats would there have been to adding vancian casting to existing characters?
I'm too sleepy for crunch, but I've been poking around this subject for a while, so I'll let you have at it while I try to go to sleep.
Okay, ToB has a 9-level system, but maneuvers also have a prerequisite. Never-the-less, we could follow the rule, that If you're capable of casting vancian spells, your caster level for non-vancian classes equals 1/2 your levels in other classes.
Prerequisite: Int 13
Benefit: You gain a single first-level spell slot, plus bonus spells based on your intelligence. You master (as per spell mastery) a single first-level spell which you can prepare and cast from these slots. You can make use of spellbooks as a wizard (vancian arcanist) would.
Is that too little? I mean, I can't see a fighter picking that feat. Unless it started a chain.
STUDENT OF THE ARCANE
Prerequisite: Vancian Magic, possessing a spellbook.
Benefit: Every time you gain a class level, you may scribe a single vancian spell to your spellbook for free. This spell represents independent study you have done in your free time. The spell cannot be of a higher level than you can cast.
IMPROVED VANCIAN MAGIC
Prerquisite: Vancian magic, Spellcraft 8 ranks.
Benefit: You gain a number of spell slots equal to half your caster level (rounded up) and can prepare spells in them. You can prepare and cast spells of spell level equal to half your caster level, but you can only prepare a maximum of two spells plus your bonus slot from having a high intelligence score at each level above first.