We can make factories that can spit out anything, but what can you do with it? How about a block that simulates an economy?
Essentially a block that accepts one item and replaces it with another. Think of the IC2 Trade-o-Mat (or ee2 condenser), but will take anything and return anything. Items and prices could be put into a configuration file, so it's easily extensible. It'd act like a chest, so mod automation (pipes, tubes, ect) can interact with it. Possibly have it work with shipments, i.e. you need to put several stacks into it before you get payment (this could simulate shipping). There could be a time disparity (configurable, random?) between shipping and payment. Currency wouldn't be a problem, because the config file. I was going to post on Minecraft Forums, but thought this would be a better place because factories.
Of course, if this already exists, I'd love to hear about it.
After thinking about it, this mod is essentially automated cheating, only good for roleplaying (which is what I intended it for).