I am trying to generate a meaningful report for business owners that reflects the system's behavior during the run of multiple groups of test cases separated in different JMX files.
I have created a make command to run all tests one by one, producing result files. However, afterwords, I don't like the idea of creating a report per file, as business owners would probably want to read just one consistent document. What is the normal approach of running multiple JMX files and producing reports?
There is Merge Results plugin which can consolidate different test executions, it's mainly designed for comparison of different test runs but you can also use it for combining the test results into a single .jtl results file.
Merge Results plugin can be installed using JMeter Plugins Manager
Alternatively if you're running tests one by one you can use the same output file via -l command-line argument so first test will create results file and subsequent tests will append new results/metrics to that file.