And I really don't see your obsession with willie fritz
IMO the Willie Fritz/Bob Davie version of the spread option is the future of college and possibly pro football. It still gives you the devastating advantage in rushing yards, but the more upright blocking and Pistol or Shotgun snap opens up whole new worlds in the passing game.
But the Flex as designed by CPJ is still a great choice if you have a size/talent disadvantage. Navy could never knock off as many Power 5 teams as they currently do if they ran the Pistol/zone option, because their best hope is to knife through a defense with the quickest-hitting plays they can run.
An under-center Flexbone team with a great defense would be like Oklahoma in the 80s or Nebraska in the 90s. They would almost never lose, but occasionally a well-versed opponent could give them trouble. A Willie Fritz team with dominant players on both sides of the ball might be almost unbeatable.