There are a couple of companies that already do this for the banks. They get all the information on longs and short trades throughout the day, from all the big investment firms, and produce a market snaphshot. One of these companies is called Dataexplorers.
Dataexplorers appears to be focused on the securities lending business, which is a tiny segment of the market compared to what the parent is proposing. Also, I see nowhere on the site where they claim to "get all the information on longs and short trades throughout the day, from all the big investment firms, and produce a market snapshot", can you please provide a reference to the place where this claim, or a similar one, is made? Most likely they are simply analyzing all long and short trades in the market on a given day to provide information about expected lending fees, which is a far cry from being able to assemble an accurate picture of the securities held by various financial institutions for their own accounts.
I used to work for them. We would recieve a huge list of the millions of trades that the big investment houses did, every single day. They only show a market snapshot, and try to make it impossible to determine what any individual company was doing - that was very important, for obvious reasons.
Banks take risk through their positions. I am arguing that they should disclose what they own to the public--not disclose aggregated risk to a sleepy regulator.
You can pay money to get this data now.
I am not sure how this would stop anything?