If the NFL decides to expand to 40 TEAMS at some point in the near future, that would result in FIVE TEAMS in all eight divisions; these would be the top candidates in my opinion {leagues in braces}:

St. Louis BattleHawks {XFL [2020 & 2023]; UFL}
Birmingham Iron {AAF}
Montreal Machine {WLAF}
Ohio Glory {WLAF}
Portland Breakers {USFL 1983}
San Antonio Wings {World Football League}
Orlando Rage {XFL [2001]}
Toronto Argonauts {Canadian Football League}

With that in mind, this would be the new team alignment (expansion teams in italics):

AFC East
Montreal Machine
New England Patriots
New York Jets
Miami Dolphins
Buffalo Bills

AFC North
Ohio Glory
Cleveland Browns
Cincinnati Bengals
Pittsburgh Steelers
Baltimore Ravens

AFC South
Birmingham Iron
Indianapolis Colts
Tennessee Titans
Jacksonville Jaguars
Houston Texans

AFC West
St. Louis BattleHawks
Los Angeles Chargers
Kansas City Chiefs
Denver Broncos
Las Vegas Raiders

NFC East
Orlando Rage
New York Giants
Washington Commanders
Philadelphia Eagles
Dallas Cowboys

NFC North
Toronto Argonauts
Chicago Bears
Detroit Lions
Green Bay Packers
Minnesota Vikings

NFC South
San Antonio Wings
Carolina Panthers
Atlanta Falcons
New Orleans Saints
Tampa Bay Buccaneers

NFC West
Portland Breakers
Los Angeles Rams
Arizona Cardinals
San Francisco 49ers
Seattle Seahawks

Also, if I were NFL Commissioner (with me being Roger Goodell's successor after he either steps down, resigns, gets removed from his position because of a scandal involving him, or flees the country), I would implement the following rule changes:

all teams having a regular season schedule of 18 games (NFL regular season of 19 weeks)
Touchbacks moved to the receiving team's own 15 yard-line
PATs moved to the 20 yard-line of the team that didn't score
Stats not counting toward the career of a player that gets ejected from a game
Victories awarded to the opposing team whenever the coach of one team gets ejected (game ends IMMEDIATELY and two points are awarded to the team that won by forfeit [three if the game is tied]; if the team that loses the game by forfeit was not in the lead when the game ended, the losing team's score is added to the team that won by forfeit and the other team's score is reduced to zero)
Delay of game penalties increased to 20 yards
Blocked punts and kicks worth four points to the defense
Interceptions worth five points to the defense
Regular kickoffs only (if the kicking team does an onside kick, that team loses two points and the kick automatically counts as a touchback [those same two points get added to the receiving team's score])
Four Extra Quarter periods if the game is tied, with each EQ period lasting five minutes