I'm sorry, my English is not the best, I hope you can understand it anyway.
My ideas are:
- A sales point like the mat on the counter, as a fixed point of sale.
- More storage space or a storage room where you can store more iron bars, gripguards or other items, behind the house would be a good place.
- The crystals in many colors and they can be dropped by customers (if they are adventurers and they can not pay with coins). Can be installed in the sword, hammer or shield with and get more money.
- Sometimes bandits should come who steal things that you have freshly ordered, if you do not allow them. This makes the stress a little more difficult to handle and stow away.
- You can color the various objects and customize them with special engravings, for example, by placing an altar or chisel station on the left side of the shop.
- The sales list remains the same, but the items do not come out of nowhere, a supplier comes and takes them (lasting 2-7 seconds).
I have more ideas, but this should be enough to implement it ^ ^