I'd treat weapons more like 'classes', with their own individual sets of feats/tricks that come with them.
Sword and Shield: Dex. Very quick and repeated attacks.
Dual Swords: Dex. Demon mode adds to it.
Longsword: Combination of dex & str. It gets just dex initially, but upon getting its 'keen' modes also adds str.
Hammer: Combination of dex & str
Greatsword: str (with multipliers for charge attacks?)
Gunlance: Con. Flat rate or maybe int/wis for its gunshots.
Lance. Con + Int/wis.
Switch axe: Str + Int/wis
Hunting Horn: cha + int/wis
Charge blade: Str + Int
Light bowgun: Dex + int/wis
Medium bowgun: Dex + int/wis
Heavy bowgun: Str + Dex + int/wis.
I'm sure I've missed some weapons, but in general the idea is that certain weapons can draw from multiple stats when playing optimally, but otherwise only get a single stat.