I've always been dissatisfied with how skills are dependent on just a single ability score, and have always felt that in reality, certain skills would involve the use of multiple faculties as opposed to just one.
So I've modified the mechanic so that skills are dependent on two ability scores: a primary ability and a secondary ability.
Let me know what you folks think about this modification? I think it rounds things out reasonably well.
The total ability related modifier would be the sum of half of the primary ability score (rounded up) and the secondary ability score (rounded down)
For example, if Intimidate is dependent on Cha and Str - with +3 modifiers for Cha and Str each, the net ability score modifier for Intimidate would be the sum of (+3 divided by 2 rounded up = ) +2 and (+3 divided by 2 rounded down = ) +1 = +3.
I think with the halves rounded up/down - the resulting numbers would be fairly compatible numerically with normal skill modifiers. This is especially important when dealing with NPC/monster skill ranks - so as to avoid restatting if you don't have the time to do so.
I've outlined a possible set of ability score dependencies below (listed as Primary/Secondary ability scores):
Acrobatics - Dex/Str
Appraise - Int/Wis
Bluff - Cha/Int
Climb - Str/Dex
Craft - Int/Wis
Displomacy - Cha/Wis
Disable Device - Dex/Int
Disguise - Cha/Int
Escape Artist - Dex/Str
Fly - Dex/Str
Handle Animal - Cha/Wis
Heal - Wis/Cha
Intimidate - Cha/Str
Knowledge - Int/Wis
Linguistics - Int/Wis
Perception - Wis/Int
Perform - Cha/Int
Profession - Wis/Int
Ride - Dex/Str
Sense Motive - Wis/Int
Sleight of Hand - Dex/Int
Spellcraft - Int/Wis
Stealth - Dex/Int
Survival - Wis/Con
Swim - Str/Dex
Use Magic Device - Cha/Int