Introduction

BG 3 inherited the Armor mechanics form DnD, where Armor Class is an abstraction that encompasses both evasion of attacks and withstanding
them due to the protective properties of your armor. It's convenient for tabletop format but is unnecessary simplistic for a video game.

Description

This mod reworks armor mechanics, separating evasion and protection, thus providing Light, Medium and Heavy Armor with more unique gameplay. Armor Class now represents only the characters ability to evade attacks. However every armor type also receives Physical Damage Reduction, which represent it's protective properties and the ability to withstand damage.

• Light Armor provides the best AC, but nearly no DR. Light Armored characters either evade the attack fully or fully suffer it. Lot's of weak attacks will eventually overwhelm them, but one or two really powerful blows can be fully evaded. Such high risk high reward strategy pushes towards having high Dexterity score and carefully managing enemies advantages/disadvantages on attacks against you while preferably not being the target at all. However, Light Armor is superior against magic users as evading a spell is easier when your movement is not obstructed.
• Heavy Armor provides great Physical Damage Resistance but low Armor Class making it easier to hit you but harder to harm. Dexterity now affects Heavy Armor AC to +1, but most of the time it's not going to be relevant. Heavy Armored characters can easily fight against a crowd of weaker enemies, withstanding their attacks and not caring this much about advantages and disadvantages against them. Their protection is stable, even though imperfect, they are likely to lose some hit points in every fight, which is helped by having high Constitution scores with little need for Dexterity. However magical attacks present bigger challenge as their damage isn't reduced by the armor.
• Medium Armor is the safe middle ground. Decent Armor Class and Physical Damage Reduction but nothing exceptional. Both good Dexterity and Constitution scores are recommended for Medium Armored Characters. Medium Armor AC is affected by Dexterity up to +3.
• Unarmored Combat is left without any changes as it's current implementation fits the logic of Armor Overhaul as it is.
  

Other changes:

• Acid. Instead of reducing Armor Class it now makes you vulnerable to Piercing, Bludgeoning and Slashing Damage. A strong counter for protective properties of the armor and generally a more dangerous effect.
• Barkskin. It's old effect would've been extremely powerful with the new Armor Mechanics, allowing to remove nearly all opportunity costs from using Heavy Armor. Also it makes less sense when Armor Class represents only evasion of attacks. So the effect got fully reworked. Now Barkskin gives +2 Physical Damage Reduction as long as the character isn't wearing Medium or Heavy Body Armor, thus making Light Armor a more preferable option for Druids.
• Draconic Resilience. For similar narrative reasons turned into +2 Physical Damage Reduction as long as you do not wear armor. Doesn't stack with Barkskin.
• Medium Armour Master Feat now gives +1 Physical Damage Reduction while wearing Medium Armor, instead of extra Dexterity contribution to AC.
• Heavy Armour Master doesn't provide extra Strength anymore and +2 Physical Damage Reduction instead of +3, which however now affects magical weapons.
• Defence Fighting Style now provides 1 Physical Damage Reduction, while wearing armor, instead of 1 AC
• Agility Fighting Style - new fighting style filling the role of of previous functionality of Defence. Provides 1 AC as long as you are not wearing Heavy Armor. Finally a usefull fighting style for multi-classing Monks. Available for Fighters, Rangers and College of Swords Bards. 
  
  

Requirements and Compatibility

Armor Overhaul requires Equipment Library for most of its functionality. It uses

EqLib_LeatherBody_Passive
EqLib_PaddedBody_Passive
EqLib_StuddedBody_Passive
EqLib_ChainShirtBody_Passive
EqLib_ScaleBody_Passive
EqLib_BreastplateBody_Passive
EqLib_HalfPlateBody_Passive
EqLib_RingMailBody_Passive
EqLib_ChainMailBody_Passive
EqLib_SplintBody_Passive
EqLib_PlateBody_Passive

If your mod also uses these passives from Equipment Library and you want to achieve compatibility with Armor Overhaul, please contact me and
we will develop a patch.

Mobility Overhaul is fully compatible and even recommended to be used together with Armor Overhaul, as it adds another interesting gameplay distinction between armor types
Weapon Overhaul is fully compatible and recommended to be used together with Armor Overhaul as they complement each other in every way
Shields Overhaul likewise fully compatible, recommended and complimentary to Armor Overhaul. Among other things, gives heavy armored characters some protection against target spells.