[SUGGESTION] [FEATURE]

Premise:

Cardboard boxes that function like single-use shulker boxes, but can be mass produced.

Possible Implementation

This is one way that the above feature may be implemented.

Cardboard boxes are to be made via sequenced assembly. A combination of adding paper/cardstock multiple times, requiring a binding agent (e.g slime), pressing, then cutting and one final press in a basin, will result in an empty, ready-to-use cardboard box.

Cardboard boxes may be placed and used as an inventory. However, they may be packaged using either slime/glue or Tape*. Once packaged, they retain their contents when broken, and may be transported or placed down, their contents inaccessible. They may be right-clicked to unpackage them, allowing their contents to be accessed.

*Tape would be a new material created using a polymer and a chemical adhesive; slime simply won't do.

Importantly, boxes should have a durability. When unpacked, the quality of the material used to package the box will determine the durability lost. If slime is used, the box is ruined and cannot be reused; it consumes all durability. Tape would only take a fraction, allowing several uses of the same box, assuming slime isn't used.

Why?

Cardboard boxes provide a thematically appropriate inventory management solution. Existing mechanics of the mod may be directly integrated into the production and usage of cardboard boxes. The proposed implementation for production of them also removes the need for an intermediary cardboard material.

Notes

• I can already of alternative & meaningful uses and caveats, such as using cardboard to package and transport structures, or having stack size restrictions for certain 'bulky' items (e.g furniture & machines). They don't even have to be discount shulker boxes, but that's the most natural solution (as there is already a desire for such a thing in the early/mid game)
• Cardboard waste handling & recycling may also be an interesting possibility; reusing spent cardboard boxes to more efficiently make new boxes.
• Keeping in line with villager torment, Tape could also be used to tie up and transport villagers and other mobs.
• If Tape isn't deemed necessary to add, box reusability could instead come from the material used to make it (e.g paper boxes having 0 reusability while cardstock ones could be used a few times)
• Cardboard tubes that make a soft 'bonk' sound when you slap something with it.

Just thought of another, maybe simpler possible implementation:

Cardboard boxes would be used instead to package any block and possibly some entities for transport. Package a chest and you can pick it up, transport it, place it elsewhere, and open it back up!

Just thought of another, maybe simpler possible implementation:

Cardboard boxes would be used instead to package any block and possibly some entities for transport. Package a chest and you can pick it up, transport it, place it elsewhere, and open it back up!

This was the first thing that popped into my head when I read your initial post. Kind of like the dolly seen in some older versions (I forget which mod).

Just thought of another, maybe simpler possible implementation:

Cardboard boxes would be used instead to package any block and possibly some entities for transport. Package a chest and you can pick it up, transport it, place it elsewhere, and open it back up!

Isn't it like the mekanism cardboard box? Still a good idea tho