The fighter is the basic battle tank.
He's the "weapon guy", the "armor guy" and the "hit point guy"
I think allowing both barbarians and rangers full access to ALL martial weapons is a diservice to the fighter.
Bring back a more agressive weapon specialization program, maybe make it just for fighters like a class ability instead of a feat, like the old 2nd edition rules, allow rangers, duelists, assasins and rgues to only take specilization in one thing (rangers for example with the bow, duelists with the rapier, asassins and rogues the dagger)
Only allow fighters and paladins to wear "extra heavy" armor ( half plate and full plate) bring back platemail as a heavy for clerics, and boost the protection of the extra heavy armors.
With the boosted hit die for rogues and wizards, fighters loose their HP edge they had at one time.
Let them get 1.5 bonus from constitution bonus (example a fighter with an 18 con would get 6 extra hit points instead of 4)
Let the fighter BAB progression increase slightly , say +6/+1 at 5th level keep the other melee classes at what they are.
The heavy armors are too restrictive, making a elven chain wearing character with an 18 dex the same or better than the heavily armored warrior.
Point blank a fighter with platemail, shield and longsword should not be touched by any other charater in the following categories:
Hit point pool
armor class
BAB
Melee damage
The exception being the barbarian that can exceed some of those points while raging, but isnt as good when not raging.
The fighter in the group should be able to hit the heavily armored dragon with his long sword when other characters cannot (the rogue may be able to sneak attack the dragon, the archer can get the dragon with a bow, but if the picked up a melee weapon and did a frontal attack ,not where near as good as the fighter)