Two-Weapon Fighting

The following rules are optional replacements for the vanilla Two-Weapon Fighting rules and the Dual Wielder feat. A player may choose to you either set of rules, but cannot actively use both or constantly switch between the two.

Vanilla Rules
When you take the Attack action and attack with a light melee weapon that you're holding in one hand, you can use a bonus action to attack with a different light melee weapon that you're holding in the other hand. You don't add your ability modifier to the damage of the bonus attack, unless that modifier is negative.

If either weapon has the thrown property, you can throw the weapon, instead of making a melee attack with it.

Dual Wielder (feat)
You master fighting with two weapons, gaining the following benefits:
 * You gain a +1 bonus to AC while you are wielding a separate melee weapon in each hand.
 * You can use two-weapon fighting even when the one-handed melee weapons you are wielding aren't light.
 * You can draw or stow two one-handed weapons when you would normally be able to draw or stow only one.

Homebrew Rules
While you are wielding a melee weapon (or a ranged weapon with the thrown property) in each hand, you can make one additional attack whenever you take the Attack action. While two-weapon fighting in this way, the following rules apply:


 * You must make at least one attack roll with each weapon you are wielding.
 * All of your attack rolls are made with a -6 penalty. This penalty is reduced to -4 if the attack is made using a weapon with the light property.
 * You don't add your ability modifier to the additional attack, unless that modifier is negative.

Dual Wielder (feat)
You master fighting with two weapons, gaining the following benefits:
 * You gain a +1 bonus to AC while you are wielding a separate melee weapon in each hand.
 * Your penalty to attack rolls while two-weapon fighting is reduced to -3 (or -2 if the weapon has the light property).
 * You can draw or stow two one-handed weapons when you would normally be able to draw or stow only one.
 * You learn the Two-Weapon fighting style. If you already know this style you may instead choose an additional style to learn from the options in the Fighter class.

Table of Penalties
Hopefull the following table clarifies the penalties caused by two-weapon fighting.

Reasoning
Two-weapon fighting has always been most popular with light, Dexterity-based classes like the Ranger, Rogue, and Monk. However, these classes (Rogue in particular) are the same classes that naturally have many class options for their Bonus Action. Since vanilla two-weapon fighting rules require the use of said Bonus Action, many characters find themselves forced to make the unfun choice between which key feature they get to use each turn. Additionally, the vanilla rules often create a no-cost situation for certain characters in which they have no reason NOT to carry a weapon in their off-hand, even if they hardly ever use it.

Under this system, characters are free to use their Bonus Actions for class abilities, while still gaining an added benefit from two-weapon fighting. Plus, with the penalty to attack rolls, not just any character can pick up a second weapon and carry it around at no cost.

DM's Note
Players often don't realize that using the rules for two-weapon fighting is NOT required to actually wield two weapons at the same time. They're merely rules outlining an option to gain an extra attack. Whenever you take the Attack action, and have the Extra Attack feature, you are not required to make every attack with the same weapon, nor is there any penalty for attacking using your off-hand.

By RAW (and by the homebrew rules above) any character can wield two melee weapons at the same time and choose which one to use each time they make an attack roll. A Fighter with Extra Attack can carry both a longsword and a mace and attack twice each turn with any combination of those two weapons. Similarly, a Rogue can carry a shortsword and a dagger and choose which one to attack with each turn, potentially alternating between the two. In either situation, all of the character's attacks would be made completely normally, with no penalties to any attack roll and with the character's ability modifier added to every damage roll.

The costs from either system only have to be paid in exchange for an extra attack not already granted by a class feature or other effect. Source