Looks interesting. I don’t understand the duping fully, is it that the shopkeeper can dupe items or that the person can dupe it or that it requires teamwork to pull off/dumb luck?
If it is the latter, possibly having a lock-out system, once the chest is under review it is locked out from any non-shopkeeper players or even just anybody but the shopkeeper accessing it.
Otherwise it looks good, the commands are bit long though, easy to remember, but some shorthand commands could be super helpful, like for po8 buying, maybe “/po8 b” or something. Just to speed it all up.
Sweet as, I am keen to use this.