Comparators do not read inventories right. SEE PICTURE. The shulker box i'm looking at has ONE item in each slot, while the one on the left has FULL STACKS of items in each slot. Yet it still outputs a signal..
Also comparators only output a signal strength of one or two when they detect a nonstackable item..
Lets see what this breaks.
Shulker box loaders/unloaders
non stackable item filters.
shulker box mass loaders(like a wall of shulker boxes that get items sorted into them)
If you need/want video/pictures please let me know