I think that's why they haven't acted on this idea. The ballpark is fan-friendly for baseball, it might lose something should they attempt to configurate it for football.
I would just build another stadium next to the Bricktown Ballpark specific for football/soccer similar to the 40,000-seat stadiums built in Las Vegas and Hartford.
Las Vegas' Sam Boyd Stadium
Sam Boyd Stadium
Hartford's Rentshlder Field Stadium:
Welcome to Rentschler Field