Some other ideas
+Conversations [Make conversation dialog with customers to improve price, waiting time, or just for some friendly chatter]
+Make customer archetypes such as a browser, questions asker, time waster, early shopper, pateint, etc
+Have multiple customers in a line up
+Customers having certain quality expectations [Such as one that wants a fancy handle or fancy blade]
+Have a hammer system that using QTE, or something like that. [Look at the papa Louie series of shop sims, or jack smiths hammer system.]
+Customer emotions [Angry when quality is bad, happy when made right or fast, upset when order denied]
+A shop rating system [The more happy your customers are, the more people will pay and more customers]
+A door ringer [Purchased in shop upgrades, would allow you to hear customers walking in while you are restocking or smelting ingots]
+Night time shoppers [Shoppers who will pay a little more, but only come at night, making sleeping not as forced as it is]
+Fatigue [The larger weapons you make the more tired you are, being more tired makes production of weaponry slower making customers upset that weapons are taking longer.]
+Passing out [Staying up too late will make you pass out, loosing daylight hours the next day]
+The ability to deny orders [I don't want to wait 120 seconds before they leave ;-;]