Every once in awhile there can be a special market or something (like a Farmer's Market or garage sale in real life). It can take place in an empty lot or even just in the Open Air Market. Players may rent a stand at a price (from some NPC or something) to sell the items that they have collected. It can look like what you see when you walk into a normal store (counter, rack, bin etc., but maybe like And then, lists items and their prices.)
Just thought it could help with more player interaction, as well as selling, buying etc. Might also make the game more realistic(?) and let characters experience being a (temporary) shop owner. It can also help get rid of the junk they've accumulated and cannot find anybody to sell to. It might also help characters take risks with their money to see if they can earn more. (Or, if business doesn't go well or add up to how much the stand was rented for, then they lose money, instead of profit) This market might put fixers out of business. So, you can make the 'market' day once or twice a year. Or, just randomly and advertise the date on the grid.
Might be complicated to code though, and the idea probably needs more elaboration, but ah well. What do you guys think?