D20 House Rule: MAD Spellcasting

A while ago I posted the beginnings of a procedurally-generated hexcrawl.  While I've neglected further postings on the matter, the project has since expanded into a programming project that implements the techniques that I was developing into a videogame.

A Sample Map of one of the many forms of the Island of Tologan-Var

While I would like to base gameplay off of the D20 rules, I've been considering implementing various tweaks.  One such idea was the implementation of Multiple Ability Dependance (MAD) for spellcasting classes: By default rules, there is only one stat that a given class has to improve in order to improve all aspects of their casting ability (Spells per day, Spell save DC, and whether or not a spell can be cast).  In this variant, each class would have two different ability scores that govern different aspects of spellcasting.


This variant has the effect of slightly weakening casters, as they now have to focus on improvement of two separate abilities, but it also allows for more variation in spellcasting characters (For example, Wizard A's charisma may give him more powerful spells, but Wizard B's higher intelligence allows her to cast more spells every day).

The tentative table of spellcasting stats looks like this:

Base Classes	Old Stat	Save DC	Bonus Spells	Casting Capablity
Bard	CHA	INT	CHA	INT
Cleric	WIS	CHA	WIS	WIS
Druid	WIS	WIS	CHA	WIS
Paladin	WIS	CHA	WIS	CHA
Ranger	WIS	WIS	WIS	INT
Sorcerer	CHA	WIS	CHA	CHA
Wizard	INT	CHA	INT	INT
Presige Classes	Old Stat	Save DC	Bonus Spells	Casting Capablity
Assassin	INT	WIS	INT	INT
Blackguard	WIS	CHA	WIS	WIS
NPC Classes	Old Stat	Save DC	Bonus Spells	Casting Capablity
Adept	WIS	WIS	WIS	WIS