Here's some suggestions I thought up while playing your game [BTW it was pretty gewd]
+Have costumers ask for a certain material [Which you could use a list to control what they buy such as you can make it so you are only selling pikes, or hammers of a certain material]
+Day shouldn't go by if the shop is closed unless a customer is inside the shop
+Add a bit more time between customers so players can take a breather
+The ability to set prices on items [If the price is 20 above cost price customers wont buy]
+Have people order things and pick them up at certain times [Set time by using a board]
+The option to expand and upgrade your shop [Two anvils, faster furnace, etc]
+An easier to use item system [You pick it up into a slot and can place/rotate it when putting it down]
+Better DOF
That's about it, I'd love to see some of these implemented. Thanks for reading!