If you pilots Mil or civil cannot cope with QFE, QNH etc how the hell do you cope with mph, knots, or kmph, or feet, metres and flight levels, or lbs per min, galls per hour, or litres per week?
Of course, no aircraft has ever taken on too little fuel because they muddled their units, and no aircraft has ever been overloaded with freight for the same reason....
Might it be better to keep things simple?