Using the NBA as an aspiring example undermines a lot of your points. Teams in that league can lose three games in every stage of the post-season and still win THE FINALS.
That's not an "apples vs oranges" comparison. The NBA playoffs are elimination series. Within each series, it is best-of-7, but each series itself is elimination.
Where is the entertainment value in 8th getting pummeled on the road by 1st?
1st vs 8th in an 18 team league is still a competitive match. And it's fairer.
Adelaide vs West Coast in week one this year (1v8) would have been a better match than the Adelaide vs GWS match (which was 1v4)
Any system that allows second chances for losing is a flawed system. Double chances are a money-making exercise, nothing more. They are just a way for the AFL to have 9 finals instead of 7. They suck and they go against the principle of what finals are about.
Finals are about performing on the day, not getting second chances for losing.