I'm pretty sure for most post graduate courses (especially in mathematics, physics, economics, finance, econometrics etc), picking easy subjects would not do you any good at all. Even if you picked easy electives to boost your GPA but the unit has absolutely no relevance to your graduate course, then the uni would not even consider you. So the system is fine as it is, if you applied for an honours in finance scholarship, the committee will ONLY consider your finance units grades, and they won't even consider your first year grades, same for mathematics, if you applied for a phd at princeton for pure mathematics but did art subjects for your undergrad electives and scored higher in them than you did in third year pure maths units, most likely the committee will not consider you. All in all, committees for post graduate entrance and scholarships are human, they WILL look at your transcript and other information rather than simply looking at a GPA measure.