With the new baseball commissioner mentioning he is in favor of expansion a while back I'm kind of shocked that the board isn't abuzz about it. I'm going to take a stab here at NFL style realignment with expansion franchises going to Charlotte and San Antonio. Yes, I know that Montreal wants a new team and out west their are options like Portland, Sacramento, and San Jose but I'm going to pass on using them for now since the last two are really only realistic as relocation spots for the A's. In doing this realignment my goal was to keep things as geographic as possible and move as few teams as possible between AL and NL. I think I found a solid way to do it that only swaps two teams that were added in the '90's--Tampa Bay and Colorado.
AL EAST: Boston, NY Yankees, Toronto, Baltimore (only change here is that Tampa moves out)
NL EAST: NY Mets, Philadelphia, Washington, Pittburgh (geographic odd balls Atlanta and Miami move out, Pittsburgh joins some teams with similar geography)
AL NORTH: Cleveland, Detroit, Chi White Sox, Minnesota (old AL Central just loses Kansas City and stays geographically compact)
NL North: Cincinnati, Chicago Cubs, Milwaukee, St Louis (old NL Central just loses Pittsburgh, still great regional travel among Midwestern teams)
AL WEST: Seattle, Oakland, LA Angels, Colorado (Texas and recent addition Houston leave for new South Division, Colorado moves in but this could just as easily be Arizona, not expanding to Portland leaves Oakland an option if the leave Northern California)
NL WEST: San Francisco, LA Dodgers, San Diego, Arizona (Colorado departs for AL to glance leagues)
AL SOUTH: Kansas City, Texas, Houston, San Antonio expansion team (Kansas City joins a trio of Texas teams for some heated rivalries)
NL SOUTH: Miami, Tampa Bay, Atlanta, Charlotte expansion team (Division rivals Atlanta and Miami are joined by Miami's instate rival and newcomer Charlotte for some heated Southeastern baseball)
Additional thoughts: The only teams making radical moves are the aforementioned Rockies and Tampa Bay but Colorado still stays within a Western region with trips to NorCal and SoCal and Seattle seems to have a similar culture as a fellow hipster haven. The Rays actually achieve some good geography and should be a strong team in that new NL South Group. The Royals and to a lesser extent the Pirates are being asked to make some changes but it's not like the other AL Central Teams were terribly close to them and playing the Texas trio makes for pretty easy travel; Pittsburgh will probably miss the Reds and Cubs but they gain a bunch of games with the Phillies and Nationals and who doesn't like a trip to the Big Apple?
Post Season: Just like the NFL--4 Division Winners plus two wild cards in each League. Top two Division winners get byes and the other two division winners play the wild card teams. Make the Wild Card Series five games with the Division winner hosting games 1-3 and wildcard teams hosting 4-5 if need be (or do 2-2-1, whatever suits you)