Is there a receptive market to this concept? Should we invest that much time in the bitcoin community? Are we going to get a frigid response from people who prefer their current favorite trading sites?
And FWIW, we wouldn't wish to put them out of business. Ideally, though, all those sites would be sharing a central trading platform so people can Sell on siteA to buyers on siteB and siteC. And the platform itself would earn a share of the commision that's large enough to support profitable operation but small enough to leave the trading site operators a comfortable profit margin.
From a user's perspective this is quite easy:
I would consider using your exchange if it would be trusted by the Bitcoin community - so that I can be pretty sure that account withdrawal actions succeed without delay or trouble and depositing money at your site would be as safe/secure as at my bank. And also very important is stability and speed of the trading site itself. Your site will definitely become a frequent target of DDoS and other attacks. In general of course there is enormous potential in creating a better site than e.a. Mt Gox.
The idea of a cross exchange protocol is quite interesting. But I guess exchanges will not help you to become a dominating central market gateway. Maybe this could be realized with an open source standard protocol - preferrably distributed.
But a more general business question: Are there not a couple of tricky regulative issues when you want to open an exchange? Do you plan to found an offshore company or something like that? Effectively you want to create something like a bank... I do not know the legal situation where you live .. but were I live this would definitely not be easy.