I was thinking of something disconnected from the actual game mechanics. Trades that could be directly involved with the game would only be cosmetic, like colored fonts for user names. The main purposes of an economy would be to add some structure to forum playing and create a ranking system based on "wealth".
Clans could benefit the most. Being able to purchase ranks would encourage players to find a means to acquire more currency. People who start roleplays could offer rewards as an incentive.
The source of the currency would offer rewards for simple task (five victory screenshots). If the simplest transaction is based on winning battle, I imagine that players with more skill would acquire more wealth.
The trick is how to balance an economy so that it can accommodate more people without creating inflation or poverty.
That said, any person, on this forum or elsewhere, can create a currency. It's value is always subjective. I tried this once with victory points in the Champion's Hall, but it was too time consuming to manage.
My next tournament will be similar but more focused with an economy in mind: It will last a month. All players will have one "point" upon entering. Players bet points on matches. Matches may be 1v1, 1v2, or 2v2. At the end of the month whoever has the most points wins.
I'll post it later, I just hope it's not to complicated.