Houserule parts

Dual Wielding
Prerequisites: Dex 15
Your penalties on attack rolls for fighting with two weapons are reduced. The penalty for your primary hand lessens by 2 and the one for your off hand lessens by 6. See Two-Weapon Fighting. In addition, When wielding a double weapon or two weapons (not including natural weapons or unarmed strikes), you gain a +1 shield bonus to your AC. If the weapon has an enhancement bonus, apply the highest to your shield AC. This takes the place of Two Weapon Fighting and Two Weapon Defense, and any feats that require these feats instead require Dual Wielding.
Improved Dual Wielding
Prerequisites: Dex 17, Dual Wielding, Base Attack Bonus +6
In addition to the standard single extra attack you get with an off-hand weapon, you get a second attack with it, albeit at a –5 penalty. Once your BAB reaches +11, you also gain a third attack with your off-hand weapon, albeit at a –10 penalty. Additionally, you add your Strength bonus to damage rolls made with your off-hand weapon normally. This feat takes the place of Improved Two Weapon Fighting, Greater Two Weapon Fighting, and Double Slice, and any feat that requires these feats instead requires Improved Dual Wielding.

Two Weapon Fighting
When using the Two Weapon Fighting mechanic, a character may make two attacks instead of one when using a standard action to make a single attack. A character may use Vital Strike with both of these attacks. When attacking in this manner, you take a -2 Penalty to all Attack Rolls, in addition to any other penalties.

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Dual Enchanting
Weapons may be enchanted as pairs, rather than individually. When enchanted in this way, the weapons become inseparable. Any mixture of One Handed and Light weapons may be paired together in this fashion. When paired, they must be used in conjunction with the Two Weapon Fighting mechanics.
Enchanting in this fashion allows for the secondary weapon to be enchanted at half the normal cost. For example, Soren decides to pair his Sickle and Dagger. In this fashion, he may make both his Sickle and Dagger (assuming they're both masterwork) +1 Flaming Weapons for a total price of 12000 GP, rather than 16000 GP.
This also benefits double weapons, allowing both ends of the weapon to be enchanted at the same time.
All weapons paired together and enchanted must always keep the same effective enchantment total. This means that a Longsword/Dagger may consist of a +2 Flaming Longsword and a +1 Unholy Dagger, but not a +1 Longsword and a +2 Dagger.