I think the problem with tanking or even just being bottom 5 is that it isn't necessarily successful and it is demoralizing to players and fans alike.
The great franchises didn't have to tank to build their team. Patriots, Packers, Steelers, Seahawks, didn't have to tank to get where they were, so is tanking really the formula for success? Jacksonville has had 6 top 5 picks in the last 6 years and look at them? Cleveland?