In real life, you can set up businesses with other people, work for businesses, take loans, use derivatives, all kinds of stuff; you aren't limited to simply buying and selling physical goods with whatever coin you have in your pocket.These options will unfortunately be limited to a few people who can afford to do so...just like in real life.
Being able to initiate high risk, high payout business maneuvers is exciting. Being able to make long term plans is exciting. Being able to actually affect the market is exciting.
I'd like to see a MMO try giving players the power to define binding economic contracts via scripts, so they are automatically enforced by the engine after players have activated them.
A simple example would be a loan agreement that needs to be activated both by Joe and Bob because it contains some actions only one of them can give permission for:
Prerequisite - Joe must have X creds. Execution - X creds are transferred from Joe to Bob at time of signing. After 5 days, if Bob has 1.1*X creds, that amount is transferred from Bob to Joe; else contract-enforcer nanomachines permakill Bob.
Such a scripting system might also let players setup joint money or asset-holding accounts with asymmetrical rights, to conditionally place some actions behind locks so they need the permission of several people, or launch scripts from account event hooks, like auto-forwarding a certain ratio of creds incoming to an account to another account. These things would pave the way towards larger player-ran companies, with sufficient transparency to be agreeable to investors but also suitably restricted to minimize damage from insiders.