What would a 4th attribute do?

I can't help but feel that universal heroes are on the way out: with only +0.45 damage per attribute, even very stat-mixing builds come out with reasonably similar damage to single-attribute heroes. It got me thinking about what could replace it. The idea of universal heroes is definitely cool, but there's an opportunity to do something equally as cool by introducing a true purple stat.

Anything too wordy or niche would feel out of place with dota's simple stat system, so here are a couple simple ones, with spitballed ideas for bonuses they could give:

• Charisma (AOE radius and status resist?)
• Wisdom (XP per minute and magic resist?)
• Luck (evasion and GPM?)
• Will (slow resist and spell amp?)

I'm pretty partial to Charisma, fits nicely into the Strength/Agility as physical and Intelligence/? as magical pattern. AOE radius also seems like a nice thing to attach to attributes, since it feels weird attached to any one item. Unsure about the secondary bonus though.