Based on some of the earlier posts in this thread, I thought of something. Try this one out:
There are three types of material: Hard, Flexible, or Soft. Hard are absolutely rigid materials, Soft are the leather/cloth types of things, and Flexible are the things in between, whether they're chain links, small scales/studs, or hardened leather (Hide).
Every armor uses a Primary type and a Secondary type (except that Soft/None is also an option, for the real wimps). Some ingredients can be used for more than one (metals can be made into chain links, which are Flexible; leathers can be Soft or Flexible, etc.), others can't (Dragon scales are not only Hard, they can only be used for armors where Hard is the primary type). Typically the Primary covers the chest and head, while the Secondary does the rest, but it can also be that the Primary covers the entire body and a small amount of Secondary is added on top or mixed in. That leads to ten combinations, each of which corresponds pretty well to an existing armor:
S/none = Padded
S/S = Leather
S/F = Studded (yes, I know studs aren't flexible, but you use so little that I wouldn't count it as Hard)
F/S = Chain Shirt
S/H = Scale
F/F = Chainmail
H/S = Breastplate
F/H = Banded
H/F = Half-Plate
H/H = Full Plate
So far so good, right? Also add into the mix a bonus/penalty for being Light, Medium, or Heavy armor. That gives 9 variables for 10 data points. Then, using a least-squares regression, I figured out the stats that best fit the book values:
PRIMARY
Soft: AC 1, MaxDEX 8, ACP +0, ASF 5%, Weight 10
Flexible: AC 2, MaxDEX 6, ACP +2, ASF 15%, Weight 20
Hard: AC 4, MaxDEX 6, ACP +3, ASF 15%, Weight 30
SECONDARY
Soft: AC +1, MaxDEX -2, ACP +0, ASF +5%, Weight +5
Flexible: AC +2, MaxDEX -3, ACP +2, ASF +10%, Weight +15
Hard: AC +3, MaxDEX -3, ACP +2, ASF +10%, Weight +20
WEIGHT
Light: no bonus or penalty
Medium: MaxDEX -1, ACP +1, ASF +5%, plus the usual speed penalties
Heavy: AC +1, MaxDEX -2, ACP +2, ASF +10%, plus the usual speed penalties
This changes a few armors; Studded and Chain Shirts are slightly worse than before, Scale and Half-Plate are much better, and most of the others only slightly changed. Chainmail is still inferior in every way to a Breastplate (except that we've raised the BP price to 400), but it at least can be made out of a single type of material instead of mixing and matching.
And there you go. If you use a material which changes the weight category, you can immediately figure out the resulting stats. Then, you can adjust for most exotic materials, by cutting the "book" benefit in half, then add the bonuses for both your Primary and Secondary. I'm rewriting my materials table to fit this system, with the Primary and Secondary bonuses separate (Primary bonuses tend to increase AC, Secondary tend to improve MaxDEX and ACP), but it might not be necessary.