Duel Wield Mastery

You have honed your ability to fight with two weapons to a fine edge - your attacks are a whirlwind of blades.

• When two-weapon fighting, when you take the Attack action, you may attack the same target with both weapons without using a bonus action. Make an attack roll for each weapon. This can be repeated for each Extra Attack. Attacking a separate target with your second weapon requires using your bonus action.
• You gain a +1 bonus to AC while you are wielding a separate melee weapon in each hand. If wearing Medium or lighter armor, this bonus increases to +2 at character level 4, +3 at level 10, and +4 at level 16. If wearing Heavy armor, this bonus instead increases to +2 at character level 12, and +3 at character level 18.
• You can use two-weapon fighting even when the one-handed melee weapons you are wielding aren't light.
• If you use two light weapons when two-weapon fighting, you add +1 to each weapon's damage roll. This bonus increases to +2 at character level 10.
• You can draw or stow two one-handed weapons when you would normally be able to draw or stow only one.

This is intended as an improvement on the PHB Duel Wielder feat, mainly with the Fighter class and Two-Weapon fighting style in mind, and has not been play tested yet. The limitations of my knowledge and/or the tool mean most of these affects will not be applied to your character automatically by D&D beyond.
Only "Ignore - Dual Wield Light Restrictions" and "+1 to AC" have been included as modifiers. Feel free to comment with suggestions on how to apply the rest. So far as I can tell there is no level gate for modifiers.