This seems quite interesting. Shame it'll most likely never happen.My suggestion to change THF would be something like this.
Two-Handed Fighting (requires Strength 15+): increases the strength bonus on two handed melee weapons to 1.75 and reduces the cooldown for cleave and great cleave by 1 second.
Improved Two-Handed Fighting (requires Strength 17+, Two-Handed Fighting, base attack bonus of +6 or higher): your critical hits now have a chance to make the target shaken (Fort DC vs critical hit damage) and reduces the cooldown for cleave and great cleave by 1 second.
Greater Two-Handed Fighting (requires Strength 17+, Base attack bonus of +11 or higher and Improved two-handed fighting): your attacks now crack the armor of opponents as if a destruction effect was on your weapon, you also gain +2 to trip and stunning blow and weapon damage while using a two handed weapon.
Superior Two-Handed fighting (requires Strength 19+, Base attack bonus of +16 or higher and greater two handed fighting): mastering the style of destroying things through brute strength you now gain twice your strength bonus while using melee weapons. Your cleave and great cleave abilities have their cooldown reduced by 1 second.
Idk, sounds ok to me. It could be even more powerful, but just allowing the feats to take the progression of x1.75, x2, x2.25, x2.5 with your strength modifier to damage.