I think that such a rigid system would prove to be a double-edged sword and would ultimately not be adopted in some institutions. It requires precise tracking of what each trader "bets" vs their losses and the application of rules to stop them from losing too much. This is data that can find its way into the outside world in the case of scandals such as this and I'm not sure investment banks would want a perfectly documented account of losses becoming public. They play a game of high-stakes risk on a daily basis, under the respectable cover of expensive premises and thick financial service books.
A friend of mine who is in what most of us would call an extremely well-paying profession told me about a highschool friend of hers who worked as a trader in London and retired at the ripe old age of 42 to live in an amazing appartment with waterfront views in central London. I was grumbling about banker-types making phenomenal money and being nowhere near as intelligent as doctors/lawyers/engineers, to which she replied, "Of course they're not the brightest, they're certainly not dumb, but they're wired different to you or I - they're risk-takers. What they do with large sums of money on a daily basis, is gambling in a casino where 'the house always wins' isn't always the case. Normal people put in their position would not take the risks they take for fear of losing"
You can potentially win big, lose or stay the same - but some of these institutions trade retirement funds or government health funds. Governments tend to have inquiries if things go wrong and not having an exacty record of how a system broke down allows the bank face while they use the trader as the scapegoat for everything that went wrong.