I'm starting a live progressive right now designed completely to eliminate benefits from and reasons for tanking (#s 3 & 4 here). There is a limit of 14 keepers, but the draft order is based on each team's most-expensive keepers. Having found in another progressive that bases draft order on salary that some owners dumped good players and kept $200K guys to improve draft position, I went with the top 8 salaries figuring that it's unlikely anyone would dump a player that good just for the possibility of a better spot; the keepers are submitted to me via sitemail, not posted until all are in, so no one knows what dollar figure will result in what draft spot. There is no trading allowed (picks or players), so no way for someone to weaken his team while stockpiling draft picks.
I set the league up that way because I was tired of playing in leagues that were decided by wholesale trading of stars for picks, leaving some teams as powerhouses and others unable to compete. That forced everyone else in the league to A) trade a bunch of picks to try to compete; B) throw up the white flag and blow up their roster to match their competitors' stockpiling of picks; or C) play the game straight up with no hope of a playoff spot and no hope of a good draft pick.
Win floors are a half-hearted option, because you can end up with 6 teams trying to win no more than 35 (40, whatever the number) games. I'm hoping the limited keepers+no incentive to tank+no trading+11 non-keepers = everyone trying to win.