Think about the game design, if tibia armors where much better no one would ever die, it's bad enough as it is, toughness increases much more then offensive power in tibia, think how easy it is for 2 level 20 to kill 1 level 20, and how insufferable easy it is for a level 100 to escape 2 level 100.The importance of armor is more related to economics, it wont make much difference for max combo potential, but it can mean the difference between farming freely or having to invest resources like runes or potions in a given hunting spot. The armors you wanna implement would make a lot of content plain trivial, and make low-level ganking groups just useless.
I'm not saying it can not be done or that it is a stupid idea but be aware of all the moving parts before you implement something so drastic.