I fully agree with the posabilities of taking the bitcoin concept to the level of stock trading. In fact, I have already proposed a complete stock exchange model, based on a modification of the bitcoin protocol and netrwork. The difference would be that a complete new network and protocol would be writen, so that all stocks, comodities or bonds, would have their own blockchain, as an independent means to float freely. Bitcoin would remain an entirely independant network, so that BTC traded for one would simply change hands and no bitcoins would ever be gained or lost by trading across this independent 'bitstock' network.