So you have three things that matter:

Weight
Heavy: Higher number is better maybe starting at around 15lbs
Light: Lower number is better maybe starting at around 2lbs

I made these numbers up. They're almost certainly at least kind of wrong.

Material:
Light: cloth, leather, energy, fur, silk,
Heavy: iron, copper, steel, all stones, ice, dragonbone, bone
Not sure: wood, mithril, adamantite, flesh,

Class
Light - You want it to say "is clothing worn on"
heavy - You want identify to say "is armor worn on"

Questions:
Is there any way, as a shaman you'd be able to figure out what was actually working? Like if I took a wood shield and an iron shield that weighed the same, would I be able to tell for sure if I was getting a bonus? If I wanted to go from my made up 2/15 lb cutoffs to something not pulled out of my ass, how would that be possible? For most stats you just get a plain number e.g. str, damroll, saves, etc. For this it seems like you just have no way of knowing at all, except in very broad "hey when I wear all dresses and veils I regen noticeably faster" sort of way.

Is there anything you could add like adding something to score? For stuff like stats you can definitely get an idea, but it seems like for this you're basically shooting in the dark. You have no idea if it's worth losing 1 str to go from 10 pounds to 20 as a heavy priest, because you have no idea how much good that 20 pounds will do. Maybe something like :

Warpriest effectiveness: none, poor, fair, good, very good, excellent, superb

How does being naked compare to wearing something appropriate for the lightpriest flavor. E.g. empty slot vs 1 ounce, cloth, clothing-class bodywear?

For heavy priests, does slot type matter. E.g. A breastplate will give a lot more heavypriestness than a glove? Do items held in hand count? If I wave around that tubing from the sanctum, am I INVINCIBLE?!