Over in Rex Invictus’ thread about their Dwarven Hammerer class The thought of giving characters extra attacks at higher levels came up to help combat types against more powerful monsters. Specifically Jard said this-
I'll bet if you more or less directly lifted multi-attack from 3.x, fighter-types still wouldn't overshadow magic users at high levels.
No moving, you have to dedicate the full action to attacking. This may or may not preclude the 5’ per cleave that you’re entitled to.
One extra attack for every 6 points your attack throw is improved by. fighting types would get an extra attack at 9, thief/cleric types at 12, mage-types never.
alternate 2) since fighting types in 3.x get +1 BAB every level, you could instead give an extra attack for every 2 full progressions of attack throw improvement (so 6 levels for fighters, 8 for cleric/thieves, 12 for mages). This would result in the fighter-types getting 3 attacks at level 12.
Ostensibly, the damage bonus fighting types get is suppose to help close the gap against powerful foes, but generally speaking +1 damage every 3 levels is going to get quickly outstripped by the 3HD (average 13.5 HP) and additional 15% chance to hit a similarly rated foe would gain. Then again, said foe is also worth substantially more XP, so maybe it balances out.
And while I personally like the idea, I may implement it in the hexcrawl I’m working on, I was wondering if anyone with a greater understanding of the rules and the relative power levels of things could chime in and help point out if it would be horribly disruptive or not.