Jeff Rients posted an interesting thought experiment on altering the core ability scores in D&D. I actually mucked around with something like this a few months back when I tried to start a bronze-age pseudo-Greek campaign. The response was overwhelming - literally! I had more players than I knew what to do with, and after a session realized that I wouldn't be able to rely on my collection of existing modules to flesh it out. So, I kind of bailed.
But that's neither here nor there. In order to promote the Greek-ish flavor, I revised the ability scores as follows:
Charisma - modifies reaction rolls, determines number and morale of followers (very important to fighters, who took advantage of phalanx-style fighting).
Favor - being favored by the gods improves Saving Throws. Being out of favor is a bad thing.
Fitness - modifies both carrying capacity and hit points per hit die, plus the usual feats of strength (busting doors and toppling statues).
Knowledge (or did I go with Reason?) - extra languages, literacy, magic
Skill - specifically "Combat Skill." The +/-1 modifier can be applied to melee attacks, ranged attacks, or armor class, chosen at creation. Particularly high or particularly low scores would apply this bonus to two or even all three options.
Yeah, I trimmed it down to just five scores. Since I wasn't using XP bonuses for high scores, and I didn't feel compelled to make Sorcerers and Witches rely on different ability scores, it just didn't make sense. If I ever go back to it, I'll probably go ahead and make Wisdom the sixth score, and have it grant XP bonuses to any class. Thus, the mechanics could play with the classic split between book-learnin' and learning through experience.