As a principal and as a progression of examination system all core high posts of civil services and alike should be fulfilled through the comprehensive and calibrated system of examinations such as CSS and recently introduced PMS where applied science,pure science, social science etc subjects conditioned as optional subjects renders the persons the men of learning across wide-spread spectrum and disciplines of knowledge or at least make him dip into broader spectrum of knowledge
Setting these typical 6 subjects as only subjects which everybody studies for many years and they alone not really broaden the horizons and that too for such important posts.
Brother you may not agree but please dont mind its my personal experience and understanding. you have every right to disagree with it, i dont want to make an issue of it with you.