I would want to open a company in Panama
No you don't want to form a company in Panama, you want to form an offshore company like US LLC and manage it from Panama.
I would want to open a company in Panama
Territorial taxation applies when a service is provided or delivered within the national territory, subject to the regular corporate income tax. However, if the work is performed outside of the country and the client is foreign, the income is exempt from taxes.No you don't want to form a company in Panama, you want to form an offshore company like US LLC and manage it from Panama.
500 is revenue? What profit should you have on minimum to consider offshore?Don't take your 500,000 USD/year business offshore just to save on taxes. You probably can't save on taxes (legally) and even if you do, I'd bet the costs of doing so aren't that much different from the costs of paying tax.
Establish your residence and business in such a way that secrecy is a non-issue.
Use nominees cleverly and carefully.
Good asset protection usually doesn't rely on secrecy
Can we get a list of such countries to see if it is worthwhile?What you said is valid for any territorial taxation country that actually cares about enforcing the law.