Instead of Superior Weapons, I'd include feats that allowed you to increase one of your weapons damage by one die size, or that added a property like High Crit or Brutal 1. So you wouldn't be wielding a better weapon, you'd be learning how to use your weapon better. To keep things balanced, there'd be a limit on how many of these "specialization" feats you'd be able to add.
I've tinkered with a very similar idea, though I've kept a few superior weapons with the caveat that one can't specialize in them (e.g. parrying dagger, double scimitar, urgrosh).
[sblock=For those who are interested]Weapon Specialization Feats
The benefits from Weapon Specialization feats do not stack. If you use a weapon where two or more benefits could be applied, you must choose which benefit to use before you attack with the weapon.
Axe Specialization
Benefit: Choose a simple or military axe. When using that weapon, your weapon damage die increases one step.
Bludgeon Specialization
Benefit: Choose a simple or military hammer, mace, or staff. When using that weapon, your weapon gains the Brutal property:
Brutal 1 for [W] = 1d6, 2d4, 2d6
Brutal 2 for [W] = 1d8, 1d10, 1d12
Bow Specialization
Benefit: Choose a simple or military bow. When using that weapon, your weapon damage die increases one step.
Crossbow Specialization
Benefit: Choose a simple or military crossbow. When using that weapon, your proficiency bonus increases by +1.
Flail Specialization
Benefit: Choose a simple or military flail. When using that weapon, your proficiency bonus increases by +1.
Heavy Blade Specialization
Benefit: Choose simple or military heavy blade. When using that weapon, your weapon damage die increases one step.
Light Blade Specialization
Benefit: Choose a simple or military light blade. When using that weapon, your weapon damage die increases one step.
Pick Specialization
Benefit: Choose a simple or military pick. When using that weapon, your weapon gains the Brutal property:
Brutal 1 for [W] = 1d6, 2d4, 2d6
Brutal 2 for [W] = 1d8, 1d10, 1d12
Sling Specialization
Benefit: Choose a simple or military sling. When using that weapon, your proficiency bonus increases by +1.
Spear Specialization
Benefit: Choose a simple or military spear. When using that weapon, your proficiency bonus increases by +1.[/sblock]