Thought of an idea, and now that there is a quest, maybe it could be a quest, like beat 1000 Orcs for example.
If you do, you get very own gollum or some kind of imp, that sells unlocked items while in battle. You could make that feature a bit penalized too, like it sells at x% lower than if you sold it manually.
Also, yes, locking items is another feature request I forgot to mention, that way i can sell all, and only unlocked items will sell in that instance. For example any sell function will not sell a locked slot.