4 scores proposal
I like the idea of 4 scores:
Toughness: Str & Con (so highly correlated in 3e anyway)
Agility: Dex
Insight: Int & "wise" part of Wis
Aura: Cha & "spirit/will" part of Wis
Melee and ranged attacks both use Dex to hit. Dex also affects initiative, Reflex, AC, and many skills, so it has plenty going for it alone.
Toughness gets the impact of both Str and Con but does not affect to hit, only damage, for melee attacks. Also for hp and Fort, and the few Str/Con skills
Aura is for character interaction stuff and Will defense, which is is used to resist things like Charm and Domination...stuff that attacks your soul/spirit/willpower, but is NOT used for seeing through illusions, noticing things, or avoiding being fooled. You can be a simpleton but of strong resolve and be hard to sway from your purpose even though easy to trick
Insight is used for everything Int is and a related new defense score, maybe called Perception, used for the same thing those new passive skills are used for (they function just like defenses anyway) along with being defense against illusions or anything involved in trickery rather than subversion of will, so the shrewdness or "aware" aspect of old Wis.
Aura is the mental/spiritual analog of physical Toughness, while Insight is the mental analog of physical Agility. So a nice sort of symmetry there.
The classic 4 classes/roles now each correspond to one ability.
Fighter/Defender: Toughness
Cleric/Leader: Aura
Rogue/Striker: Agility
Wizard/Controller: Insight
Not sure I would actually use this because I don't know if it's worth the effort of dealing with all the cascading, downstream consequences for the game system, but I've been thinking along these lines since I stopped playing D&D toward the end of last summer. In know it's not 3 scores but it's still a substantial reduction and I think in some ways it may be more elegant if you want to keep to some of the archetypes of the old (and new system). What do you think?