I wonder how this would work in play:
D20 Combat made simple.
Basic precept: weapons are a special effect for doing damage in combat; the weapons themselves may have special qualities which affect the damage and the rate of damage.
Basic Damage
All weapons do damage according to the HD of the current class of the wielder. Thus a mage does 1d4 no matter the weapon and a barbarian 1d12 no matter the weapon. Observation: the base damage of the weapon, no matter the weapon, quickly becomes secondary to the various additions from feats, magic etc. Rationalisation: a fighter multiclassing to wizard is concentrating on spellcasting, not combat; classes like Eldritch Knight make up for this with BAB which can be converted to damage with Power Attack.
All classes of weapons are abolished except for exotic weapons, each of which requires a feat as before. Non-proficiency is represented by the reduced die of damage.
All manoeuver feats (e.g. Cleave, Improved Sunder, Improved Trip, Manyshot, the TWF tree) remain the same.
The feats Weapon Focus, Weapon Specialisation, Melee Weapon Mastery, Greater Weapon Focus, and Greater Weapon Mastery, and other similar feats are replaced by a single feat, Combat Improvement, which grants +1 to hit and +1 to damage. This feat stacks with itself.
Damage is increased by modifiers from Strength, magic, etc. A weapon wielded in both hands gets 2x Strength bonus. There is no 'secondary' hand: a character wielding two weapons gets his full Str bonus on each. Note that TWF penalties apply unless the appropriate feats are taken.
All special weapon properties (e.g. Shocking Burst, Holy) remain specific to the weapon and affect damage as before. (Design note: people enjoy special qualities and rolling dice.)
Criticals
All weapons threaten critical on a roll of 20. Criticals are confirmed as before. Magic weapons have a critical range equal to the Plus of the weapon. Note: This makes the Greater Magic Weapon spell much more viable
The Improved Critical feat increases the critical range by 1. It can be taken multiple times and it stacks with itself. It has the prerequisite that Combat Improvement must have been taken twice.
Power Attack
Prerequisite: Str 13.
Benefit: On your action, before making attack rolls for a round, you may choose to subtract a number from all attack rolls and add the same number to all damage rolls. (But see Ranged Weapons below). This number may not exceed your base attack bonus. The penalty on attacks and bonus on damage apply until your next turn. There is no special bonus or penalty for the size or handling of the weapon.
Ranged Weapons
Ranged weapons that are thrown (e.g. Spear, Javelin, Hand Axe) benefit from all the above feats.
Ranged weapons that directly use muscle-power to launch projectiles (e.g. Atlatl, Slings) benefit from all the above feats.
Ranged weapons that indirectly use muscle-power to launch projectiles (e.g. Longbow, Crossbow) must make a Fort save as if unattended vs DC15+extra damage unless specifically constructed (q.v. Strength bows).
How's that for a start?