In short: This patch mod will redistribute the stat penalties to be less severe with helmets and more severe with body armor.

In vanilla, each armor piece (helmet, body, legs) will penalize you in equal amounts.  This makes helmets more burdensome in comparison to the body armor despite using much less material and being targeted less often in combat.

With this mod: Wearing the entire set of armor will still incur the same penalty as vanilla, but will punish you less for wearing just a helmet or leggings since these are targeted less than the body in combat.

This is based on the initial calculation of taking damage as explained here on the wiki.  Helmets will incur 20% of the overall penalty of the set, while Leggings will harbor 30% and Body Armor will grant the remaining 50% to match the chance that armor is targeted in an attack.

Compatibility

This change necessitates replacing the entire "statModifierbyType" entry with new targets, so any mod that points at the old targets won't work.

Works perfectly with mods that change or add other stats like Warm Armor as well as mods that change the crafting recipe.

Does not work with mods that tweak or nulifies the same penalties.

Mods that changes both penalties and other stats like Armor Overhaul will only half work, as my changes will overwrite theirs.

This only affects vanilla armors.  Mod-added armors will retain the same penalty ratio and needs a seperate patch to conform.

If another mod uses the same operation to replaces the same "statModifierbyType" entry, Im not sure what would happen.

Notes

The tooltip in-game will round decimal points down, so while the penalty is a near perfect 50%/30%/20% split in caculations, the tooltip for armor may not reflect this perfectly.  For instance, the Lamellar Armor movement penalty is -1.8%/-2.7%/-4.5% for helmets, legs, and body respectively, the tooltip will show 1%/2%/4% instead.  The Character Window should show the resulting penalty more correctly however.

This is a mod I made for me to use.  If you personally would like something tweaked such as removing archery penalty, I would suggest you open up this mod and change it to your heart's content.  You can even publish it on this site if you feel others will benefit with or without credit to me, as the code is too simple for me to claim.

Credit

I put this mod together thanks to viewing the codes of mods like Armor Warm and Armor Overhaul.