Iron Chest

Crafted with 1 chest, 7 iron, and 1 empty map.

By default, copper golems will not try to sort into or from an iron chest; copper golems will ignore an iron chest. This can be something a player can toggle by alt-clicking on the chest, up to Mojang. If thats all that comes from this suggestion, that would be enough.

Iron Chests have less storage space to counterbalance the following utility.

Each square of storage for an Iron Chest can be toggled like a crafter. If an item is in that space when the square is toggled, the item is "silhouette stamped" onto that space and any time a player quick sorts or a hopper feeds into the chest, the matching item will go to that space first. The Iron Chest effectively remembers what items are allowed to be stored into it.