It lets each caster be different, but ties the type of spell to a stat. It also doesn't diminish the caster by not using a non prime stat to cast with. I haven't fleshed it out fully yet but I like the way it appears. Any problems leap to anyone?
I don't see any problems. I actually plan to do something similar.
The "magic" will essentially be the same, the only thing that varies is how each individual is able to access it. If you learn to manipulate magical energies through formulas and equations, you use Int. If you summon the power through your inner strength or innate ability, you use Cha. If you use the spirits or natural forces around you (fire, earth, water, air), you use Wis.
I don't really plan on having separate spell list although there may be some tendencies, like Int-based magic being more destructive, Cha-based having more enchantments, and Wis-based affecting nature and the elements.
I also might make each one a separate feat to add to their uniqueness.
Related question: what's a good way to "introduce" magic into the campaign besides having the players finding a tome of spells? What about the player that wants to be more like a sorcerer or a shaman?
For Cha/sorc magic, I was thinking of creating some kind of "magical aptitude" table that each player rolls on to determine if they have some innate ability. They can then choose to develop that ability (taking the feats, etc) if they choose. For Wis/shaman, maybe they would have to find a teacher and meet some kind of requriements. My world will also have various human tribes so if they choose one of them, perhaps they have a stronger connection to the natural and spiritual world.