There is no way to alter an item's appearance or tooltip or actual bonuses in combat or over time.
However, let's say an item gives you UnitStat_IsUsingSpecialHammer=1. Then you have a spell that targets that specific unitstat through a calculation. So there you have a viable combat alternative. You can't use it to curse armor outside the battle, but you can use it to give a hammer extra damage or take away something from it.
