Starting in either 2012 or 2013, MLB will add an extra Wild Card team to each league. Both wild card teams will play a one game playoff and the winner will go into the playoffs. In essence this is really still 8 playoff teams.
The way I would do it, is there are 10 playoff teams, 2 wild cards per league. But instead of the one game playoff, I would give the team with the best record a first round bye. This rewards the best team, and it doesn't punish the better wild card team.
Ideally, I want 2 leagues, each with 15 teams. The top 5 teams from each league would make the playoffs. No more divisions. I suppose the main purpose of divisions is because of time zone differences and rivalries, so if there would be a way to keep them in tact I would, but I don't want divisions having any effect on who makes the playoffs.