A friend of mine had a good idea about armor wearing restrictions. He proposed
that a character's ability to wear types of armor be based on their defense
skill. This way you could put a defense rating requirement on each type of
armor. The rationale being that it takes a certain amount of martial training
in order to fight effectively in various types of armor. Just to throw some
numbers out as examples, lets say:

Defense Skill 0 is sufficient for cloth, 20 for patchwork and leather, 50 for
Banded and Chain, 100 for Plate. (Magical Equivalents like netted, woven,
rubicite would require further consideration, and this is BY NO MEANS anything
more than an illustration, no change is being suggested here).

Yet another way to approach this is to make each armor type a skill which would
modify how well a certain armor worked for a character.

I think both are good ideas, but the current system is good enough.