I like the discussion. Because you're right, if you're between 4th and 5th place going into the playoffs, and you have no hope of competing with the top teams in the league (which is usually the case), there is no reason not to try and tank. More money, better draft pick, still get 2 games a week for training purposes.
I'm not sure how easy it would be to program in percentages of salaries for specific weeks, but it certainly sounds reasonable. On the owner's side, what about adding an incentive to win playoff games like there with Cup games. So even if you're in 4th place, you can CT to try and win your $50K (or whatever) reward. This could dissuade the attempt to intentionally lose games.
This thread should probably get moved to the suggestions forum.