36-team idea: grant expansion franchises to Los Angles, Mexico City, Portland and San Antonio. Realign into 6 divisions of 6 teams each. No more AFC or NFC, doing away with conferences altogether.
East Division: Buffalo, Carolina, Cincinnati, Cleveland, Detroit and Pittsburgh.
South Division: Atlanta, Jacksonville, Miami, New Orleans, Tampa Bay and Tennessee.
North Division: Chicago, Green Bay, Indianapolis, Kansas City, Minnesota and Saint Louis.
West Division: Arizona, Dallas, Denver, Houston, Mexico City and San Antonio.
Pacific Division: Los Angeles, Oakland, Portland, San Diego, San Francisco and Seattle.
The 16-game regular season could be maintained, with each division playing one other division per season, or a 17th game at a neutral site could easily be added. Adding another bye week for each team makes sense, as does expanding rosters from 53 to 60 players, including 50 active per game, plus 15-man practice squads. The off-season limit should also be increased from 90 to 100.
The post-season could be contracted to 10 teams, giving all 6 division winners a 1st round bye, or it could be expanded to as many as 16 teams, including 10 wild cards. Since conferences are eliminated, any 2 teams, even from the same division, could meet in the Super Bowl.
I think adding one expansion franchise per year makes the most sense. Instead of having expansion drafts of veteran players, I prefer giving each expansion team 75 total selections in the annual college draft before their inaugural season, even though that obviously means less selections for established teams, unless the total number of selections is increased from 256 to 355 or more.
40-team idea: grant expansion franchises to Anaheim, Las Vegas, Oklahoma City and Salt Lake City. Realign back into 8 divisions of 5 teams each. Conferences could either be reinstituted or not.
Atlantic Division: New England, New York Giants and Jets, Philadelphia and Washington.
Northeast Division: Baltimore, Buffalo, Cincinnati, Cleveland and Pittsburgh.
Southeast Division: Atlanta, Carolina, Jacksonville, Miami and Tampa Bay.
Central Division: Chicago, Detroit, Green Bay, Indianapolis and Minnesota.
Metro Division: Kansas City, New Orleans, Oklahoma City, Saint Louis and Tennessee.
Southeast Division: Arizona, Dallas, Houston, Mexico City and San Antonio.
Northwest Division: Denver, Las Vegas, Portland, Salt Lake City and Seattle.
Pacific Division: Anaheim, Los Angeles, Oakland, San Diego and San Francisco.
Expanding the regular season to 18 games would make sense, as each division would play 2 other divisions per season. Expanding the playoffs to 16 teams would also be appropriate. The Super Bowl should be played on a Saturday, never later than February 26th.