By just wearing the armor, you should level its skill overtime. It makes sense, you get used to using it and you build the strength to move around with it at ease. I makes a whole lot more sense than equipping it and getting beat up. Not only that, but it's a pretty risky thing to level up your armor when you can be attacked at any time and wounds don't recover very fast. That feature can still remain, but this alternative would be very helpful and reasonable.