Need a supported way to change default setup in PTL, dynamically.

With more and more features getting added, as a developer I want to test my changes with already existing PTL tests. But, sometimes default setup that PTL provides does not really enable the new features that are getting added.

There needs to be a supported way of describing a given setup to PTL and make PTL use that setup as default setup before running any PTL script. This will help in developer testing and finding out bugs when two features interact with each other.