The US, UK, AU, NZ and CA are entirely different countries because they take their laws really seriously. In other countries what may be legal for a politician is strictly illegal for everyone else.
The loophole that Mr. Soros were using is a "bit" different then what you're saying about Brazil. That loophole allowed hedge fund managers whose funds were widely held (had several investors in the fund and he had a minority stake only) to defer tax payments on the performance fees that the manager received. His original capital that he injected into the fund was fully taxable throughout the years.
There are a couple of billionaires in Brazil. Why are they not using foreign entities? There was Eike Batista with a large fortune. Why he was not using a foreign entity to avoid taxes altogether?
Seriously, I got what you're trying to say but it's still unbelievable. My income is fairly big compared to the average Joe therefore I'm a bit hesitant to try this out. I'd be seriously worried what if one day a politician wakes up and he gets envy of my lifestyle and tells the tax authorities to check if my foreign companies has any local sourced income and guess what, I'd fail on the tests as trading income is locally sourced, always.
Btw you put the bug in the ear so I'll ask a Brazilian advisor about this.