I like
the idea of armor by the piece, because that's the way real people do armor. For one, it takes a wealthy person to get a full suit custom made and fitted all at once (I know an SCA fighter who spent over $1000 on a suit of full plate), for two, just because you want inflexible steel at knees, elbows and head doesn't mean you want inflexible steel at waist and neck. You may, you may not, your fighting style dictates whether protection or mobility is the higher priority for a given area. I fought 2-handed sword, it was vital to me to be able to go backwards faster than a guy with a sword and shield could go forwards (a 2-handed sword has a
minimum range), so I cut the encumbrance and inflexibility to the bare minimum.
That said, I
dislike armor by the piece because it abandons the distinction ICE made from day one between DB, which is the ability to avoid getting hit in the first place, and AT, which is the ability of a particular type of surface to soak up and dissipate the energy of a blow.
Trust me, if I could think of a mechanic that would reconcile the two, I'd have already shared it.