We have Crop Hoppers, Tier 1, 2, and 3
I propose "Shop Hoppers", (I claim the trade mark!) , with different tier levels.

Put a Shop Hopper on the bottom of any barrel or chest and it will automatically sell to the server anything that currently can be sold at "Warp Shop or Shop "

Different tier levels could for example sell to the Server at varying prices depending on the hopper level. The lowest level "Shop Hopper" would have the worst sell price to the server and the highest level Shop Hopper would give the best price.

Items sold through the Shop Hopper would sell below the "Warp Shop" prices. The reduced price being compensation for not having to go to Warp shop and spend time selling there.
Shop Hoppers could also have restrictions, like one type being only able to sell "Mob Drops" Another type to sell cooked meat, and yet another type for Farm produce, Beets, Potatoes, Sugar Cane, etc.
Shop Hoppers in my opinion could also help reduce lag by lowering the amount of hoppers used in automatic chest storage systems.
Reducing those chains of chests connected by hoppers to just a single hopper feeding into a chest or barrel with a "Shop Hopper" I think would free up some bandwidth for gameplay