Issue #25514: Consistency change to Fortify Heavy and Light effects
The Fortify Heavy and Light armor effects from potions and enchantments are strangely set apart in how they work from the other fortify effects, in that they raise the skill level value directly instead of the modifier and power modifier versions that the other effects use.
The player-exclusive perks AlchemySkillBoosts and PerkSkillBoosts control the effects that these modifier actor values have on the player, and they do have an effect defined for the armor ones. But the way they are set, using the Mod Incoming Damage entry function and checking for WornHasKeyword, they would reduce incoming additional damage by the percentage just for wearing one piece of armor with the corresponding keyword. So if somehow raising one of those actor values to 100, wearing a piece of armor would make the player immune to physical attacks, disconnected from armor rating.
Now it's true this may as well be left as is given that increasing the skill level directly in effects does have an effect on armor rating, those weird perk effects won't come into play, and it can even work for NPCs that way. But when looking at the Survival Mode CC plugin, there's the Brown Rot disease which as it turns out does lower the Light and Heavy Modifier actor values. With the result that unless patched, the player will have physical damage on him increased by 25, 50 or 75% if having the standard, severe or crippling Brown Rot respectively and wearing just one piece of light or heavy armor, and by those percentages squared if wearing pieces of both light and heavy armor. Possibly making it better to wear no armor when affected by brown rot.
But that particular bug aside, I would propose patching the perks and effects here, just for consistency with the rest of the fortify effects. I've changed the perks so that the modifier actor values will only increase the armor rating of the armor pieces with the corresponding heavy or light keyword by the stated percentage. And I've changed the enchantment and alchemy magic effects to use the modifier and power modifier actor values, and their descriptions to state what they do. The USSEP already changed all these to fix some other bugs, so it's not even touching new records. Attached is the file if my explanations can convince you.
Armor Modifier Fix.zip