The best solution would be the addition of a "junk bag,"
You can already do that. Place items you want to sell in a basket/crate, and then sell the container all at once for the value of the contents.
+1 to this, it makes the game 100% more enjoyable. You just need to get into the habit of stashing that useless loot into a barrel. I use barrels because they are the common and don't weigh too much.
I use backpacks to store important +skill gear and scrolls, baskets to store crafting reagents, and barrels to store vendor junk. That way I never accidentally sell a container full of important things to a vendor.
