Wow, after I read your post I went back 5 years and compared some of the stats and what it would result to (let me know if you want some raw data, and I will send)...
Your wildcard idea is GREAT! Especially if you like or must have 6 teams in playoffs. My only downfall is that in fantasy football once you make the playoffs its all up in the air. You could easily get a wildcard spot while in 4th place in the division just from having highest points tally (two of the last 5 years showed that could happen). After that, putting a 3 win streak would grant you the championship
With as hard as the playoffs are in fantasy football, I dont like 60% of the league making the playoffs, it takes a lot out of the regular season games.
One more thing I would recommend is to make the tie breaker scenarios of who advances very clear before the start of the season. We currently use head to head records (adds even more value to regular season games, especially interconferance), then points for, then points against.