This must happen, it is unfair to the NL teams to have to compete with more teams for the same number of playoff slots. The Brewers should be the ones to switch, but I'd have no problem with the Astros moving over.
The playoffs will then be expanded to six team from each league. Over the course of 19 days, each team will play each other team three times on consecutive days, with four off days between each series. The team that wins the most games goes to the WS, with a single elimination playoff for ties. The NL and AL will start their playoffs one day after the other, so that each day there is a minimum of three games being played and a maximum of six. Lots and lots of games each day, with a premium on deep starting rotations and bullpens, and a chance for teams that get off to a bad start to fight their way back.
The top seeds will have four home series (12 games), the 2nd and third seeds will have three home series, the 4th and 5th will have two, and the 6th will have one home series, providing a great advantage to the regular season winners.