"The WTS thinks that you should not sue a JW who defrauds you"
If JWs really must deal with JW owned businesses, they should cover their butts by only dealing with incorporated entities owned by other JWs, not with the other JWs directly. That way they can say: "I'm not suing Brother Jones, but Brother Jones LLC*!" Even better if you have your own company. Always deal through that, then you have a lawsuit between two companies.
* In Australia (and I think South Africa), it would be Pty. Ltd. In the UK I believe it would be LTD.