Many great modding opportunities could be had if this were possible. Let me be clear: When an equipment: armor weapon jewelry etc is equipped, it triggers a spell effect When the same equipment armor etc is removed, it triggers a different spell effect this spell effect triggers would instantaneously on equip/removal and would use the player's action for that turn.
This would allow cursed items into the game. Maybe a hidden flag that isn't revealed until the item is equipped? Also items from chests of evil have a higher chance to be cursed. And of course blessed items on the opposite side of the spectrum.
Not exactly a "hidden flag", phasmy - just something people wouldn't know about unless the creator of items in question decided to put in the description. But for the record, I think that is a great way to start with item sets (though we do have a way to do that already, but it's less elegant).