It seems the law is that you can open an arbitrage company, but that would require you to put money into the business and be accepted then still by a bank as a customer. Other ways are by piggy backing on existing companies who do import/export and put the money on top. That is though then very suspicious and I think will get you into Money Laundry investigation in no time.
I have been doing as such Arbitrage with China now, only about 6%, but that pretty consecutive and wiring about 20k back daily.
There is not premium with China now.. its actually cheaper there.