Here is an armour idea.
It's based on the idea that I am sure people have tossed around before, that armour takes a quasi "wield" level to wear it. SImplest way would be based on level. 5% chanting per level of char. Could be total level or a classes main leveling area or whatevers.
So, with scaleable caps on amount of magic per piece we could find a reason to diversify in armour types at earlier levels if you give things like cloth armour a different % magic on it.
To explain. Chanting laen with *6 m fort uses what, 12.5% or whatevers. Chanting cloth could take 4% for *6 m fort or 6% m fort.
Leather goods would be in between cloth and metals, etc...