I wrote this for fun to address some long-standing thematic, language, and corner case issues with the two-weapon fighting rules. It also allows you to finally two-hand a weapon and use armor spikes at the same time.
Two-Weapon Fighting
You can two-weapon fight as a full-attack action while wielding more than one weapon. While two-weapon fighting, you can make one additional off-hand attack using another light or one-handed weapon you are wielding. You may only add half your Strength modifier to the damage rolls of off-hand attacks. If your primary attack uses a two-handed weapon, you only add your full Strength modifier instead of 1-1/2 times your Strength bonus to the damage roll.
Your attacks take a -6 penalty until the end of your turn. The Two-Fighting Fighting feat and using light off-hand weapon each cumulatively reduce this penalty by 2.
If you are a creature with more than two hands, you gain an extra off-hand attack for each additional off-hand you possess while two-weapon fighting. You do not need to make these extra attacks using weapons carried in your off-hands, but each attack requires the use of an additional wielded weapon.