Is there a way to test brain activity/aptitude on a measurable scale in order to identify a suitable occupational aptitude? It seems individuals are able to adjust their cognitive aptitude to some degree through nurture, which is controlled by various elements such as environment and conditioning. However, they're stuck with their nature - heredity. Is it possible to measure and compare one's capacities to occupational cognitive demands?
According to the United States Armed Forces, it is possible. They do something similar to what you propose with the Armed Services Vocational Aptitude Battery. However, according to the section "Test Validity" of the linked Wikipedia article, there is some debate about whether it only measures literacy or IQ.