I have suggested a playoff system, in which teams from different leagues and divisions compete for some additional promotion opportunities. In addition, it would give all teams at least 3 to 4 playoff quality games. It would require one additional week in the season.
Classification
Teams within each league would be classified into 3 categories based on their regular season record:
(1) Top 4, including the two conference champions, and the two other teams with the best record (so in your case, it would include 3 teams from the Great 8). These teams would play in a pair of best-of-3 series to determine the league champion, who would automatically promote. As the other 3 teams are eliminated, they would join the 2nd chance playoffs.
(2) The 4 other teams that finish 2nd-4th. These teams would be placed in an inter-league 2nd-chance playoffs for an extra opportunity to promote. They would be joined by teams from the 1st category that are eliminated, and would eventually challenge teams from the division above to promote.
(3) The 8 teams that finish 5th-8th, would play in a relegation league. Each team would play a game against each team in the opposite conference, effectively completing a home-and-home series with those teams - game locations would be determined based on where the teams played during the regular season. The standings for relegation league would include the 10 regular season games between against other teams, plus the 4 games played during the playoffs. The bottom 4 teams would relegate. The next two would have to defeat challengers from the division below to remain in their league. The top 2, would remain in their currrent league.
The schedule:
Week 1
1) Championship semifinals, best-of-3, Tuesday, Saturday, (Sunday)
2) 2nd chance mini-league. 4 teams from different leagues would play 3 games, with the winner in each mini-league continuing their promotion opportunity. Games would be played on Tuesday, Saturday, Tuesday.
3) Relegation classification. Bottom 8 teams play 4 games which are added to their regular season records against the other 7 teams. Games would be played Tuesday, Saturday, Tuesday, Saturday.
Week 2
1) Championship finals, best-of-3, Tuesday, Saturday, (Sunday). Winner promotes.
2) 2nd chance qualification knockout. 3 rounds to determine 2nd chance teams.
Tuesday: Completion of 2nd chance mini-league. Losers of championship semifinals against another semifinal loser from another league.
Thursday: Winners of 2nd chance mini-league play a winner of a Tuesday game between semifinal losers.
Saturday: Winners from Thursday.
3) Relegation classification. 3rd and 4th games.
Week 3
2nd chance playoffs. Two rounds knockout. Teams involved are the 11th and 12th place teams from each league in the upper division, losers of the championship finals from each league in the lower division; and teams advancing from the 2nd chance knockout.
Games are played on Tuesday and Saturday. Winners promote to upper division, or retain their place in lower division.
Opportunity:
Teams that enter the 2nd chance mini-league would need to win 7 games to promote (possibly 6, if they can win the mini-league with a 2-1 record).
Losers of championship semifinals would need to win 5 games to promote.
Losers of championship finals would need to win 2 games to promote (plus win their championship semifinal).
11th and 12th place teams would have to win 2 games to avoid relegation (plus finish 3rd or 4th among the bottom 8 teams in their league).