Currently, weapons with +1 get wc+1, and armor (including shields) with +1 get ac+1. An interesting method of differentiating different playstyles could be:

One-handed weapons and shields continue to receive the traditional wc+1 and ac+1, respectively. Two handed weapons get divided into two camps:

• Two-handed greatswords, clubs, or other “heavy” weapons receive wc+2 for every +1 on the weapon. This reflects how very heavy weapons can be difficult to block or parry.
• Split weapons (dual swords, etc) and polearms (lucerne hammer, poleaxe, halberds) receive wc+1 and ac+1 for every +1 on the weapon. This reflects that these weapons are specifically designed for additional defensive options.

This does leave a final category: two handed defensive “weapons”. This doesn't really exist at the moment, but I could conceive a case or two where a two-handed item gets ac+2 for every +1 on the item. This could happen with a large two-handed shield, and one player in a party could play a “tank” role during a very tough enemy fight.