I run a Swords and Wizardry Complete game without weapon proficiencies. This is because I hate them, and find them pointless. I want wizards to use swords, for everyone to wave guns around, and for people to select weapons that express some element of their character's personality or style rather than because they're proficient with it. As readers of this blog know, I am strongly influenced by Runequest, where everyone casts spells and waves swords around, and I wanted to introduce this feature to D&D.
Without weapon proficiencies, one of the few advantages fighters and fighting-man classes have is removed. I am not bothered by its removal, since it's such a minor advantage that it barely qualifies as such. I have been considering replacing it with an ability that represents the fighter's training and expertise but that is also a significant and distinct advantage over other classes using weapons. I think that this expertise is not represented in the main mechanical use of the fighter's expertise, which is making attack rolls and dealing damage. I think in S&W Complete, the ranger and paladin already have enough advantages to compensate for this reduction, but the fighter doesn't really (though I do find S&W does a better job balancing the fighter with other classes. I would not be opposed to extending it to rangers and paladins in games with stat minimums to qualify for those classes (something I do not use). Here is my proposal to compensate the fighter:
A fighter using a weapon upgrades the damage dice he rolls on a successful attack by one type using the following progression.
I prefer this system to static bonuses because it upgrades both average damage and maximum damage each time. It also incentivises the fighter to attack and press the offense, instead of just tanking for thieves and wizards, by making them attack specialists.