Yeah, Ive lived in Panama for bout three months... that would be a great place to trade and live without a doubt, cost of living is low comparably. Ive never heard of trading fimrs in Panama, but if there are some good ones...I might consider that myself!
Except for tax reasons there is no reason you need a firm in Panama. With great internet access you can use any broker you want to trade. Have you considered that? I am clueless about laws regarding U.S. citizens trading from outside the U.S. but despite that issue, you can use IB, OX, ToS TradeStation or anyone else to trade from Panama. Even with capital gains taxes, you will still live like a king down there. I will eventually buy a house and spend some time during the year there as well.