A few ideas that other people have mentioned... and some others

1.) Four game series --
Advantage-- adds 8 weeks to regular season.
Disadvantage-- I think the unproductive time may only be about 6-7 weeks so this solutiion may eat up too MUCH of the calendar.

The other disadvantage to this method is that new leagues which start in June or July would never be able to catch up with other leagues. With the layoff most new leagues catch up by the 2nd or 3rd year.

2.) All Star break --
Intriguing idea... would give a 1 week vacation in middle of season. Although not sure that really does much.

P.S. I love the suggestion of league voting for an all-star team

3.) Lengthen season by 1 week and bring schedule to 162 games.
Interesting thought... but again unless we come up with several ideas that each use up 1 week we aren't getting anywhere.

3A.) A twist on ideas 1 and 3. How about we extend the season and mix 4 and 5 games/week schedules. Maybe something like a 36 week season with 18 5-game weeks and 18 4-game weeks. For extra realism 4-game weeks could contain an off day.
Haven't come up with a good algorithm for how to distribute the games but something like this might work

Division Foes: four 4-game series against each --- Total 12 5-game series - 60 games
Non-Div Foes: two 5-game series against each ---- Total 16 4-game series - 64 games
Interleague: six 5-game series and two 4-game series. - 38 games.

Problems are-- Unbalanced Interleague Schedule (but it isn't really balanced now anyway)
I don't like that many Interleague games

Nevertheless a new twist to look at.

4.) STAGGER seasons. For example have leagues 1-15 start on April 1 and leagues 15-?? start on May 1. This would be really nice for people who own multiple teams because you would always have action. Just about the time the trading deadline hits in leagues 1-15 the pre-deadline spurt in the other leagues would hit. I really LOVE this idea.... but I suspect we will never see it because it would involve more setup time for PB staff.