Rule: Double-stat saving throws
Replaces: Standard saving throw ability modifiers
In Use In: None thus far
Synopsis: Each save depends on two stats instead of one
Double-Stat Saving ThrowsEdit
There is a corollary between strength and hardiness, as well as between quick hands and quick thinking. The saving throw structure as it exists right now is keyed off a single stat, but there is justification for having each save benefit from two stats.
A person's "toughness" is a function both of their hardiness as well as their strength. Indeed, becoming stronger generally goes hand-in-hand with greater endurance, better health, and resistance to injury. Thus, it is reasonable to base Fortitude on Strength and Constitution rather than only Constitution.
A creature who is preternaturally quick will still be caught off-guard if he is not also quick-thinking. Likewise, a person who is clumsy but quick-thinking might still have enough time to protect himself from, say, falling rocks. Thus, Reflex saves can depend on Intelligence as readily as they can on Dexterity. (Arguably Wisdom, also, but sometimes the situations in which Reflex saves come up aren't defeatable by foresight.)
Additionally, this puts forth the idea that creatures without an Intelligence score automatically fail Reflex saves. This is justifiable, as an ooze or a giant centipede simply doesn't have the presence of mind to recognize that a wizard casting a fireball is a threat to be avoided until it is far too late.
Will saves are derived from Wisdom, but a person's resistance to coercion and mental stress has as much to do with their force of personality as it does their insight and depth of thinking. A high Charisma can equate to an excess of pride and a surfeit of personal resolve, which is very applicable to a person's Will save.
The impact of this rule would be that saving throw bonuses would almost unilaterally increase, as most creatures have positives in most of these areas. Mindless things would become easier to kill, which isn't necessarily a bad thing; however, since save DCs would be higher, player casters might become frustrated at the rate at which their spells were resisted.
Another effect would be that players might be less inclined to dump certain ability scores (*cough* Charisma), as doing so would now have an effect on their Will saves.
Alternative: Better of the TwoEdit
An alternative, one that doesn't have such a profound effect on the game's numbers, would be to simply use the better of the two scores for each save. This is the approach favored by 4th edition, but might work here as well.