Let's face it Interleague play is here to stay. Which I am ok with. I don't care about the All-Star game anymore and I want a solution to the home field advantage in the playoffs.
The league will not be expanding anytime soon, so we have to make it work with 30 teams. I propose a realignment, I would like to see 6 divisions of 5 teams. So each league would still have 3 division champs and a wild card. It would allow for more common opponents with the Interleague format. It would mean there would always be an Interleague series going on. The easiest way to realign would be to ship the Astros to the AL West.
In my format you would play your division teams 18 times each. You would play all the other NL (or AL depending on which league your team is in) teams 6 times each. Then the teams would play 30 Interleague games, this could go 2 ways. First option each year divisions would matchup and they would play home & home. This option would make the playing field fair, everybody would have common opponents. It would mean the Cubs would only play the White Sox every third year but it would also ensure the Cubs go to Fenway and Yankee Stadium every third year. Or you could follow the current Interleague schedule and keep having the problem of 2 more NL teams than AL teams which makes for difficulty in scheduling.
In my format you could use the Interleague record to decide home field if you want or you could use the most logical and reward it to the team with the best record.