I think trading works, in that it involves a "system" and the ability to spot something and anticipate cause and effect.
i.e. In March of 2003 I anticipated a housing bubble
In 2001 I anticipated stagnant wages for a decade.
In May of 2006 I anticipated the financial crisis
Just spotting items in news stories and having the ISTP internal magician pull outcomes together without any applied thought.
Reasoning for stagnant wages was pretty simple. Increased immigration in conjunction with manufacturing, technical and customer services roles being outsourced in mass. If one isn't making something you can't really create wealth.
Reasoning for the housing bubble, changes in lending standards in conjunction with CDS driving a loosening of standards.
Reasoning for anticipating the financial crisis. The Federal Reserve stopped publishing M3, and other related data that indicated the short term lending facility balance sheets weren't "pretty."
Rather simplistic and "gut" responses however later shown to be "spot on."
So yes, I think an ISTP could be good at trading.