muyuu,
I am working on the math right now of how to use the miners as a sort of MCMC to asses the money supply. Derivation is proving a little more than I had anticipated. I will list it in full on statisticaleconomcis.org when I am done. Allows for a floating money supply using network information and the self interest of the miners.
As for the implementation of the stock exchange, rather stock certificates. I will likely type that up as a paper and similarly post. I do not have the coding ability to embark on such an adventure.