We would have the option of 'zip' and 'unzip' to change the bag's zip status.
A bag with an open zipper would function like the bags we have now.
A bag with a closed zipper would not allow random drops to go into it.
Contents of zipped bags can be viewed by players with eyeballery or eyeballery 2.
If we drag an item onto a zipped bag the bag will automatically unzip to accommodate the item.