This is an interesting discussion, and I don't necessarily disagree with you, but in reality it comes down to a dog-and-pony show as much as anything else. I found the following which has average football viewers in 2021 to get an idea of the teams and to work to segregate into the "Yes", "Maybe" and "No" in order to get to your Top 48 options.
https://medium.com/run-it-back-with-zach/which-college-football-programs-were-the-most-watched-in-2021-49ef4f315858
Some assumptions I make are that SEC and Big 10 all get in (no change to current membership) and while I love the military academies, and Navy and Army have the eyeballs in top 48, they don't make the cut. One thing that is in question is what about basketball schools? I throw some into "Maybe" that certainly don't make it based on football alone (Kansas, Duke).
The number next to them is their average football viewership from the link above.
So who are your nine Maybe's to make the cut?
YES (39)
Ohio State — 5.22M, Michigan — 4.74M, Alabama — 4.64M, Penn State — 3.87M, Georgia — 3.61M, Oklahoma — 3.46M, Auburn — 3.22M, Michigan State — 2.89M, Notre Dame — 2.84M, Oregon — 2.57M, Wisconsin — 2.41M, Nebraska — 2.29M, Texas — 2.26M, Florida — 2.21M, Arkansas — 2.03M, LSU — 1.90M, Texas A&M — 1.86M, Mississippi — 1.81M, Clemson — 1.74M, Iowa — 1.64M, Purdue — 1.63M, Oklahoma State — 1.58M, Tennessee — 1.51M, Minnesota — 1.28M, Florida State — 1.27M, Indiana — 1.24M, UCLA — 1.18M, Illinois — 1.13M, Southern Cal — 1.11M, Kentucky — 1.08M, Miami — 1.038M, Maryland — 971K, Mississippi State — 858K, Stanford — 778K (if they want in I think they are in), Northwestern — 716K, South Carolina — 575K, Rutgers — 488K, Missouri — 462K, Vanderbilt — 37K
So there are 9 from the Maybe list to get to 48.
MAYBE (30)
Iowa State — 1.219M, Cincinnati — 1.216M, Baylor — 1.16M (I say F'em), North Carolina — 1.032M (with basketball I think they get in), Utah — 994K, Washington — 985K, West Virginia — 948K, TCU — 907K, BYU — 893K, Texas Tech — 798K, Arizona State — 739K, Boise State — 657K, Kansas State — 636K, Louisville — 616K, Virginia — 611K, Pittsburgh — 550K, Kansas — 540K (Without basketball they are a hard no), Wake Forest — 526K, NC State — 525K, Washington State — 483K, Georgia Tech — 459K, Virginia Tech — 447K, UCF — 407K, Colorado — 366K, Arizona — 337K (need basketball to matter to be considered), Louisiana — 334K (basketball helps push them up a lot), Oregon State — 321K, South Florida — 303K, California — 222K (I think if they push they get it), Duke — 64K (need basketball to matter to be considered),
NO
Navy — 1.039M, Army — 804K , Tulsa — 358K, Tulane — 356K, East Carolina — 301K, Air Force — 255K, Appalachian State — 241K, Houston — 232K, Coastal Carolina — 223K, Syracuse — 219K, San Diego State — 198K, Memphis — 193K, Western Michigan — 171K, SMU — 164K, UAB — 163K, Northern Illinois — 163K, Boston College — 156K, Hawaii — 139K, Ohio — 130K, Eastern Michigan — 122K, Buffalo — 119K, Kent State — 117K, Temple — 112.7K, Ball State — 112.6K, Western Kentucky — 97K, Utah State — 91K, Akron — 90K, Marshall — 85K, Nevada — 78K, UTEP — 63K, Colorado State — 59K, San Jose State — 59K, UTSA — 51.9K, Georgia State — 51.7K, ULM — 50K, Fresno State — 45K, Wyoming — 38K, UNLV — 34K, South Alabama — 26K, New Mexico — 25K, Troy — 24K