...why not just bump up the damage die he rolls with weapons by one step? If they're already doing that for racial classes, it's not a big deal to do it again. Obviously, they'd have to be careful about stacking this effect (the dwarven fighter would go from 2d6 to 2d8 damage), but I'm not seeing how it's going to bust the game wide open to make sure the fighter is mowing through enemies.