To add a new twist to "the economic game," I propose the addition of vendybots that would offer items for sale in a little more flexible manner than is now possible with vending SDBs. Specifically: For a seller, depositing items into the vendybot would work a lot like putting items into a cabinet of SDBs, but in addition to setting a price for each item, a seller also could set a batch limit for each item. For a buyer, a vendybot would display multiple items for sale much like a street vendor, but showing how many of each item could be purchased as well as the price.
Vendybots would co-exist with Auction House and vending SDBs. Unlike these, however, vendybots would not make their contents knowable via the API. To find out what a player's vendybot had for sale, one would actually have to visit that player's street and interact with the vendybot.
It would be cool if vendybots could make announcements like gnomes and also log who made purchases (like butlers log street visitors, but accurate). It would be super cool if vendybots also could be taught to buy as well as sell.