I've been reading some posts out there and thinking about this for some months. I've also done some playtesting and I have come to this:
1. The fighter should be valuable because of his or her class abilities and not because of his or her equipment.
2. The fighter should also be useful out of combat.
3. The fighter should never just panick and run away from combat.
In order to do that.
I suggest:
1. Instead of weapon focus/specialization feats
Skill at arms: A competence bonus to hit and damage at 2,5,8,11,14,17,20 so he or she is still a threat with a simple club or dagger at any level.
Half DR: The fighter is able to bypass enemy defenses by finding weak spots. At level 10 the enemy's DR is reduced by one quarter regardless of being extraordinary or supernatural. At level 15 the enemy's DR is reduced by half.
AoO: At level 7, enemies provoke AoOs as if they were unarmed unless they have weapon focus for the given weapon or natural weapon or uncanny dodge. At level 14 all enemies provoke AoO as if they were unarmed unless they have uncanny dodge or 4 fighter levels.
Quick attack: At level 9 a fighter may make an extra attack at -8 penalty as a free action once per round and only in a round he or she doesn`t use a full attack. The penalty is -4 with a light weapon or a crossbow and -12 with a two handed weapon.
Block:A fighter has a 10%+1%/level chance to block every enemy attack with a weapon or a shield. If the attack is blocked it targets the weapon or shield used to block it instead negating any critical hits and dealing damage to the weapon and shield as a sunder attack, any excess damage is dealt to the fighter and the weapon or shield may be destroyed. Ranged attacks can only be blocked with a shield. A tower shield or a rapier grants a +10% bonus, these bonuses do not stack. Any condition that negates dex bonus to armor class also negate this ability.
2. Add diplomacy, knowledge(History, local, nobility and royalty), profession(sailor, navigator) and use rope. Also add the logistics ability to increase the party's or the army's overland speed at level 10.
3. Bravery: A fighter never panicks or cowers, any time he or she would panick or cower, he or she is shaken instead. Being brave is not just not being afraid, but facing your fear.