Want Baseball to be more interesting late in the season? Take a page from the European soccer leagues, and drop the bottom five major league teams to the minors and move five top performing minor league clubs up to the majors. Crappy major league teams will have to stop phoning it in a the end of the season to keep from being relegated, and the prize for winning a minor league pennant will be all the sweeter.
Add to this the fact that different mid-sized cities will be getting major league teams every year, and you'll see a real renaissance of interest in baseball in places like Buffalo, Rochester, Durham, Richmond, Norfolk, Omaha and Sacramento. Not only will teams have the chance to play in the majors if they work hard enough, but team owners will have to keep stadiums ready for the majors. Better facilities can only help attract fans (well, maybe not, judging from the Washington Nationals season this year, but it should hold as a general rule....)