I could live with one more playoff team, but here's what I would do:
I would make both leagues 15 teams, no divisions, top 5 make the playoffs. Yes, there would be interleague games going all the time. 90 series total. Either 1 or 3 series going on throughout the season. 3 x 20=60; 1 x 30=30
You play everyone in your own league 10 games = 140, 6 home/4 road vs 6 teams; 4 home/6 road vs 6 teams; 5 home/5 road vs 2 teams.
Each team plays 18 interleague games, for a 158 game schedule. I don't like interleague, but it's not going away. Obviously, the natural rivalries would continue to play each other every year.
Season would be 25 1/2 weeks=158 games in 178 days.
At the end of the season, the 4 and 5 seeds play each other best of 3 to face the one seed. That would make teams really go for the one seed, since they'll be facing a team that really had to burn out their best pitchers to make it to the next round.
The main reason why they should eliminate divisions is to free the Orioles and Blue Jays from the Yankees and Red Sox. Even the Rays could be returning to badness, so get them out of that division, and just make 5 out of 15 make the playoffs with basically a balanced schedule.