I forgot to implement a off-hand weapon parry mechanic in the HR above, though. Perhaps something like this:
Two-Weapon Fighting
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, but you can't use this bonus attack to target a creature you already attacked during your Attack action. You don’t add your ability modifier to the damage of the bonus attack, unless that modifier is negative.
If you have the Extra Attack feature, you can make as many attacks with your Two-Weapon Fighting bonus action as you can make with your Attack action.
If either weapon has the thrown property, you can throw the weapon, instead of making a melee attack with it.
Alternatively, you can give up your bonus attack (or attacks) and use your other melee weapon to parry. If you do so, until the start of your next turn, you have a +2 bonus to AC against melee attacks.
I'm well aware that these kind of small circumstantial bonuses are against 5e's general design philosophy of keeping everything dirt simple, but eh, personally I don't mind.