A big problem with 2nd edition is that weapon combat styles are gated behind class walls, and that weapon proficiency level really doesn't mean much. These two problems can be solved together by adding a new type of class feat, the weapon style feat, that would be available to all classes. These feats would give some decent base ability, but also scale up to be even better as you gained proficiency. I've come up with some ideas for these:
Melee Power Attack Weapon Feat 2
Trained in weapon: 1 extra damage die
Expert in weapon: Increase the Damage Dice for the Weapon One Step (this does not affect deadly and the like)
Master in weapon: 2 extra damage die
Legendary in weapon: 3 extra damage die
Two-Handed Melee Cleave Weapon Feat 2
Trained in weapon: One Action: Attack, if you hit, attack adjacent enemy at a -2
Expert in weapon: Two Actions: Attack, if you hit, attack enemy in reach at -2, continue to do so for other enemies in reach so long as you hit (no enemy twice)
Master in weapon: Two Actions: Same as above, though you may choose to add an action to this to Step during the process (choose when you start to move).
Legendary in weapon: Two Actions: Same as above, though you may choose to add an action to this to Stride during the process (choose when you start to move).
Ranged Multishot Weapon Feat 2*
Trained in weapon: Two Actions: Make two attack rolls at a -2 on same target
Expert in weapon: Two Actions: Make two attack rolls at a -2 on any target, may choose to add an action to make one additional attack at a -4.
Master in weapon: Two Actions: Make two attack rolls at a -2 on any target, may choose to add an action to make two additional attack at a -4.
Legendary in weapon: Two Actions: Make two attack rolls at a -2 on any target, may choose to add an action to make three additional attack at a -4.
Two-weapons Multislice* Weapon Feat 2
Trained in weapons: Two Actions: Make two attack rolls at a -2 on same target.
Expert in weapons: Two Actions: Make two attack rolls at a -2 on any target, may choose to add an action to make one additional attack at a -4, may combine the damage.
Master in weapons: Two Actions: Make two attack rolls at a -2 on any target, may choose to add an action to make two additional attack at a -4, may combine the damage.
Legendary in weapons: Two Actions: Make two attack rolls at a -2 on any target, may choose to add an action to make two additional attacks at a -4 and take a single Step Action, may combine the damage.
* For Agile Weapons, reduce the -4 penalty to -3.
These are just proposals, but they make getting the next level of proficiency *exciting*, and not just a bland +1 to your attacks. They also serve the purpose of opening up combat styles across the board (though those with lower proficiency won't be *as* good).
Note that there's a couple styles missing here (one-handed and sword and shield, namely), and I think the same thing needs to be done with Armor proficiencies as well, and probably also spellcasting proficiency (making metamagic tied to your training in a particular spell area).
